500 Internal Server Error is a generic error message, given when no more specific message is suitable. This is one of the most frustrating errors that can occur. It never has a straightforward solution.
The cause most likely occurs due a wrong rules on the .htaccess file.
.htaccess File :
If you are using Admin Tools the .htaccess on your site, it may be interfering with loading of the live chat scripts. Please double check the .htaccess configuration. Any syntax errors will cause a 500 Internal Server Error and the chat module do not displayed.
To confirm whether a misconfiguration .htaccess is the cause of the 500 Internal Server error, either remove or rename the .htaccess file temporarily and then try to reload the page.
Two rules that cause problems with the chat module :
#RewriteRule ^(components|modules|templates|images|plugins|media|libraries|media/jui/fonts)/ - [F]
#RewriteRule (.*\.php)$ - [F]p>