You can debug the issue if you can access your wp-config.php file by adding the following:
define( 'WP_DEBUG', true ); define( 'WP_DEBUG_DISPLAY', false ); define( 'WP_DEBUG_LOG', true );
This will put any errors your site generates into a log file called debug.log in the wp-content – this should then tell you where the error is coming from. You can also just set WP_DEBUG to true and WP_DEBUG_DISPLAY to true and get the error directly on your website page (but this will expose the error to the public).