You can view the exact problem in your Error Log, Under cPanel -> Logs, it will give you information about while folders/files and settings are causing the error.
- If you see "is writeable by group" please follow setup 1 below.
- Also if you see "Invalid command 'php_value', perhaps misspelled or defined by a module not included in the server configuration" please follow step 3 below.
If you are running a PHP-based script on your site and are receiving a 500 and/or 404 errors on your pages, it is likely you have one or more of the following occurring:
1. The permissions on some of the folders or files are 777 or 666. If this is the case, change them to either 755 or 644 in Cpanel's File Manager (or using your local FTP client).
2. The files and/or folders are not owned by you. Certain applications having been run under php as an apache module may have files owned by the apache user of nobody. An indication that you don't own the files would be if you are unable to change their file permissions. To correct this, please contact support (firstname.lastname@example.org) and provide the location of the folder or files that need to have your ownership.
3. The selected PHP version is not compatible with your website. Please login to cPanel and go to 'Select PHP version' to select a PHP version compatible with your website.