A problem may appear suddenly, and/or have been caused by your own actions like updates and install of new elements...
Causes can be more or less easy to find, this require concentration, patience, and methodology...
In the latter case, go back and consult your editor help documentation, forum, webmaster, regarding a specific error messages, and environment requirements
Remember : "the right solution can only come from the right diagnostic..."

NB : if in doubt, it is always possible also to check if only you are affected by the problem :
- check real-time server status here : https:/support.yoorshop.hosting/serverstatus.php 
- you can use a web proxy like this to check and see if you have a local cache issue or conclude that there is truly a problem:
http://hidebuzz.com 

How to debug ?
Activate the debug modules of your CMS if there are any
Look at the 'errors' section of your cPanel to get started (htaccess error, test with a blank .htaccess to find out).
Enable the log_errors, and display_errors modes from your cPanel, find icon "Select PHP version", and on the right go to "switch to php options".
After, test your website to see if messages are displayed, and check also the error_log file at the root of your account in :
/home/youruser/logs/php_error_log
AND/OR in error log file folder of the addon domain/subdomain to see if any errors are written.
Website problems/incompatibility of a PHP element, test different PHP versions/PHP extensions

If you use PHP-FPM on cloudlinux servers (in your cPanel, presence of icon : 'PHP selector'), you must switch back temporarily to PROXY mode :
https://support.yoorshop.hosting/knowledgebase/3931/How-to-configure-a-site-with-NGINX-PHP-FPM.html and enable the log_errors, and display_errors modes as described above at line number 3

If you are under cPanel servers (in your cPanel, presence of icon : 'MultiPHP manager') :
From MultiPHP ini editor, go to editor mode, activate display_errors and log_errors by adding this :
log_errors = On
display_errors = On

Note : once debug ended, you must deactivate debug modes for security reasons of your website...

Error name resolved (ERR_NAME_RESOLUTION_FAILED, DNS_PROBE_FINISHED_NXDOMAIN, DNS_PROBE_FINISHED_BAD_CONFIG)

If you have added, bought or transferred a domain to us, you must check that the nameservers DNS are the ones linked to your hosting account. Check email related to your Hosting service 'Informations about your hosting account', and check values you must use at section : 'Dns Informations : name servers'

Check that your domain is pointing to the IP of our server, see at bottom WWW A: https://intodns.com/ 

Check that your domain has not expired at your registrar, or by a whois site like: https://www.whois.net/
(look for Expiry Date, attention, the format is in English: MM/DD/YEAR)

Blank pages alias error 500
See debug process at top of page

'Error 403 forbidden'

First of all, verify that the asked path/URL is correct, and make sure you have at least an index file, index.html or index.php, or similar... Indeed, when you you just have subscribed to our service, you must upload your files by FTP in public_html folder for the main domain of your cPanel account, or the corresponding folder if this is an addon domain or subdomain.
Or, this is a permission problem folder / file, this sometimes happens after manipulations on your side or after FTP upload too.
Permissions must be 755 for folders, and 644 for files within each folder containing your website.
The folders such as public_html / subdomain folders / addon domains folders, must remain in them 750.

'404 page not found'
This type of problem is 99% to a website problem, the page link is improper rangeland, the page does not exist really too, setting a syntax problem of rewriting rules (rewrite), even a module can cause this...

If after restore with jetbackup manager, you get error 500 :
- you must delete file class_index.php in cache folder
- put back native files in /classes/cache/

For API locks, or else :
https://support.yoorshop.hosting/knowledgebase/3421/How-to-disable-Nginx-default-security-rules.html

Error 'Sorry!, your website has moved'
You see that message following to an account suspension or after IP of your site has changed
The cache or network as you take a little time, this will rule alone in a short time normally, otherwise clean your cache Ctrl + F5, if persist restart your router and your computer. Contact us if still persist after 4-8 hours.

Pictures are not displaying
Error 410 : pictures/pages are not all displaying
It is possible that some web URLs are taken in our block referrer traffic system. Contact us....
OR
Some images are not displayed and no information :
Use 'Inspect Element' of your browser and see if it is a PageSpeed format. The PageSpeed optimization system can cause path problems according to the site. See article related.
OR
If using Nginx-FPM, deactivate browser cache by XtendWeb in your cPanel : set expire header

Error 502 'bad gateway' or Webservice currently unavailable Error 502
This is a server error due to apache or nginx having a temporary issue, it can happen sometimes quickly and shortly, but contact us if this persist...

In case you use PHP-FPM with Nginx, the issue is due to an excess of process of your website, either internal PHP, either external with high traffic spike (attack if not natural). Our monitoring script is checking this issue every 5 minutes, and will fix if needed.

Error Country is blocked
Blocked visitor is redirected to : https://hostingfilters.com/banspam/country.html
Check our dedicated article for solution : https://support.yoorshop.hosting/knowledgebase/2464/IP-block-by-country.html
We use these error codes to monitor the fight against spam and for security :
- 206 : partial content displayed, is a consequence of an issue with our code 410 below, contact us. Beware that it is absolutely normal to have a certain inherent number of 206 in your logs, this is due to load of external resources.
- 405 : requests which looks abnormal, types : frame/xss/injection SQL/http.
- 406 : requests which looks abnormal of all types, if in section visitors of cPanel, you see much 406 on user agent : Serf/1.3.8 mod_pagespeed/, this probably means a conflict with your website, try disable pagespeed : see our related article to proceed...
- 410 : URL referrers (russian, chinese websites and others) or keywords blocked. If some pages on your website don't display correctly, contact us, an issue can be confirmed by presence of error code 206 which would increase.
- 429 : Number of requests has been limited by our system on delicate files like wp-login.php, but not only.
- 444 : To stop bots, and attempts to delicate files like config.php files.
- 499 : Visitor or client has not answered the server request in time, connection is closed simply. It can be re-opened the next second in case it was a network issue. Excessive connections from one IP can cause this too...
- 503 : Too many requests, can be used by anti ddos plugins, but also by our server security...

Cache issues with backoffice Prestashop, or display updated articles on your website
Indeed a native cache for back-office is activated, you can find how to disable on prestashop forum.
Normally the updates should appear within seconds on your website, try this to bypass your cache browser : CTRL + SHIFT + R, if it persists, this means your cache is conflicting, delete your cache folder so that it rebuilds itself with fresh data.
Also, see the 8th post to disable the cache back-office :
https://www.prestashop.com/forums/topic/335988-backoffice-pages-dont-refresh-after-any-modification


Prestashop backoffice slow down (temporary in general) :

https://www.yoorshop.hosting/announcements/2381/Prestashop-back-office-slow-down.html

To check resource usage live, simply check column right of your cPanel, do page refresh to update...
Or, you can use also SSH without the need to refresh and to see more details about processes...

To see real-time the use of your processor, you must use SSH with software putty, type command :
/usr/bin/top -d 00.50
Open another shell window with putty
You can check what is doing one process, by his PID number, if 22596, type :
strace -p 22596

To kill all processes :
type in your SSH console : kill -15 -1 , and press Enter
(this will turn off also your SSH session, reconnect to SSH, and top again to see that all came down)

SQLSTATE[HY000] [2002] Can\'t connect to MySQL server on \'127.0.0.1

Use localhost as host in config file, not 127.0.0.1, check that 127.0.0.1 is allowed in the 'mysql remote' section of your cPanel

Clear all files in cache of app and modules, or error will still show on some parts

 

ERR_TOO_MANY_REDIRECTS

This is related to a conflicting or erroneous redirection problem in the htaccess file, whether or not linked to a module. Consult the publisher's documentation or your webmaster. Go back on your last changes while waiting for the solution.

A php window open when going to website

An incorrect php value is causing this in your htaccess, remove partially or totally content of htaccess

And/or : at root of your cPanel account : home/youruser/, make sure htaccess file contains this :
################

<IfModule mod_deflate.c>
SetOutputFilter DEFLATE
<IfModule mod_setenvif.c>
# Netscape 4.x has some problems...
BrowserMatch ^Mozilla/4 gzip-only-text/html

# Netscape 4.06-4.08 have some more problems
BrowserMatch ^Mozilla/4\.0[678] no-gzip

# MSIE masquerades as Netscape, but it is fine
# BrowserMatch \bMSIE !no-gzip !gzip-only-text/html

# NOTE: Due to a bug in mod_setenvif up to Apache 2.0.48
# the above regex won't work. You can use the following
# workaround to get the desired effect:
BrowserMatch \bMSI[E] !no-gzip !gzip-only-text/html

# Don't compress images
SetEnvIfNoCase Request_URI .(?:gif|jpe?g|png)$ no-gzip dont-vary
</IfModule>

<IfModule mod_headers.c>
# Make sure proxies don't deliver the wrong content
Header append Vary User-Agent env=!dont-vary
</IfModule>
</IfModule>

##########

Remove this or similar if needed and present, from htaccess of your website files :
AddHandler php5-script .php .htm 

Tips to know :
To clear your local cache, do CRTL + F5
To load website from server without loading cache ! CTRL + SHIFT + R
Try using another web browser if it persists...

WebDAV not working

With app Nextcloud, You get error like : "Your web server is not yet properly set up to allow file synchronization, because the WebDAV interface seems to be broken."

Change profile Nginx to 'YOORshop defaut cloud'

 

Read also :
https://support.yoorshop.hosting/knowledgebase/1201/How-to-check-the-resources-used-in-cPanel.html

Various issues

If you see strange codes appearing on your site, or at install issue prestashop 1.7 with Softaculous with error : 

• Could not gather sufficient data to generate new cookie key (new_cookie_key). Please make sure your domain is pointing to this server and there is no .htaccess file restricing access to your domain

Turn off in php.ini this : short_open_tag (short open tag)
(ref : https://support.yoorshop.hosting/knowledgebase/115/Can-I-customize-my-phpini.html )

For fileinfo, this is by PHP extensions :

https://support.yoorshop.hosting/knowledgebase/1100/PHP-versions-extensions-and-cache.html

 

Prestashop web services :

 

Apache forbids by security the use of PUT and DELETE requests

In order to be able to use this type of remote requests, you must use a rewrite method, here is the example of the principle below (this requires a webmaster). Information is valid for default config NGINX : PROXY mode, but use template : "YOORshop defaut cloud"

 

Create a file named put.php with this content :

 

$putdata = fopen("php://input", "r");

$file="your_filename.txt";

$fp = fopen($file, "w");

while ($data = fread($putdata, 1024)){

    fwrite($fp, $data);

}

 

fclose($fp);

fclose($putdata);

 

Put this in file .htaccess :

 

RewriteEngine on

RewriteCond %{REQUEST_FILENAME} -s [OR]

RewriteCond %{REQUEST_FILENAME} -l [OR]

RewriteCond %{REQUEST_FILENAME} -d

RewriteRule ^.+$ - [NC,L]

RewriteCond %{REQUEST_METHOD} (PUT|DELETE)

RewriteRule .* put.php

 

In your admin/ web service configuration, enable CGI. (After performing the tests, if still problem, ask us for verification of CGI activation)

 

Prefer local delete by phpmyadmin if possible or import your website and use any LAMP

 

Security of your website

Our CXS security tool will inform you in real time of blocked injection attempts, or infected files, security breaches, and malware. The deep scan on all the files in your account is also carried out every two weeks...

 

You can have a very basic assessement with such online tools, they are poorly reliable because they don't have access to inner files of sites :

https://pentest-tools.com/website-vulnerability-scanning/website-scanner

https://www.immuniweb.com/websec/

This one can be good : https://quttera.com/website-malware-scanner