In almost all cases a Internal Server 500 error on our servers indicates that you have incorrect file/directory permissions set. This may be due to someone with access to your files adjusting them without realizing the implications or a script that you’re running modifying them without your knowledge.
You can resolve this error by ensuring your file/folder permissions are set correctly. All files should be 644 and folders 755. One exception to this is configuration files (such as Joomla’s configuration.php) which should have file permissions set to 640. Once set correctly, you should not need to adjust them again. You can reset your file/directory permissions in bulk via FTP.
If this does not resolve your issue the remaining possibilities for the cause of the 500 error are: 1) you have invalid directives in your .htaccess file(s) which you’ll need to fix, or 2) a PHP script that you’re running is corrupted.
Please do not hesitate to open a technical support ticket if this article does not resolve your issue.