It looks like you faced a fatal error. You need to see what the errors are. Guessing what might be the problem and trying different solutions may lead to even more trouble. The first step is to enable debugging. You can add a few lines to the site’s wp-config.php file. With the error log enabled, you will see the actual problem.
To enable it, open your wp-config.php file and look for define(‘WP_DEBUG’, false);. Change it to:
define('WP_DEBUG', true);
To enable the error logging to a file on the server, you need to add yet one more similar line:
define( 'WP_DEBUG_LOG', true );
The errors will be saved to a debug.log log file inside the /wp-content/directory.
