In order to get to the bottom of the problem, I need to see the logs from the server. You can retrieve them via your hosting panel (please refer to your hoster if you don’t know where to get them) - this option actually is preferable, or you can add the following code to the beginning of the page that is not working (after <?php tag):
ini_set('display_errors', '1'); ini_set('display_startup_errors', '1'); error_reporting(E_ALL);
then reload the page. If there’s an error message appeared, please share it while reporting the issue, if not - use option 1. I won’t be helping unless logs are provided.
Please, while sharing the logs, make sure you have removed sensitive data (passwords, logins, etc.).
After troubleshooting, don’t forget to remove the lines you added.
Double (or triple, if needed) check that you have uploaded all the files to your webserver.