To Check the Issue which PHP error causing this issue please Follow the below steps:
1: Login to your Cpanel, click on File manager and go to Public_html.
2: Then create the new .htaccess file under your domain root folder or you can also use the existing .htaccess file.
3: Add the below coding in your .htaccess file to check the Logs of error which are causing your site to give the error HTTP 500 error: