Sometimes you will encounter the 500 error when use a feature of theme or a plugin. To identify which causes the error, please follow 3 steps below:
1. Open file wp-config.php in the root folder of your website (you will need to login to Cpanel >> File Manager tool, or login to file server with FTP client software), then replace this line:
define( 'WP_DEBUG', false );
define('WP_DEBUG', true); define('WP_DEBUG_DISPLAY', true); define('WP_DEBUG_LOG', true);
Then save the file.
2. Reuse the feature which causes problem (to catch the error).
3. The detail error message will appear.
After finishing, please undo step 1.