When something breaks, WordPress can write PHP errors to a log file with WP_DEBUG.
Do not leave debug logging on forever. The log can include paths and other sensitive details. Turn it off when you finish.
Enable logging (hide errors on the front end)
Edit wp-config.php and set:
ini_set( 'display_errors', 'Off' );
define( 'WP_DEBUG', true );
define( 'WP_DEBUG_LOG', true );
define( 'WP_DEBUG_DISPLAY', false );Reproduce the problem, then open /wp-content/debug.log via FTP or the host file manager. Search for security-ninja or FATAL. Notices and warnings are useful, but fatal errors are what stop the page from loading.
Also see Fix errors showing on the frontend.
When you are done, set WP_DEBUG to false, and delete or protect debug.log.
