If your WordPress website produces a 500 internal server error, it means the machinery of WordPress is not working properly.
Fear not, with WordPress debug it might not be that hard to resolve the error.
Turn on WordPress debug.
You’ll need access to your website’s file system to turn on WordPress debug. Normally this is done through your web hosting control panel’s File Manager. If you don’t have access to this, you’ll need FTP access to your website. Ask your web host how to set this up.
Once you have access to your website’s file system, find the file called wp-config.php. Download this file and back a backup of it somewhere safe. Download another copy of this file to a different location, and make the following change:
Save the file and upload it to your web hosting file space, overwriting the existing file.
Now reload your website and check the error message to give you a clue about what the error is.
If you see there is a problem caused by a file in a plugin or theme, it’s best to remove that plugin or theme temporarily, and let the plugin or theme author know what the error is.
You may also need to change the PHP version of your website through your web hosting control panel. In a cPanel hosting control panel, this is done through “Select PHP Version”.