A rare issue can happen when using CloudLinux + mod_lsapi which causes the following error:
Your PHP installation appears to be missing the MySQL extension which is required by WordPress
If PHP 7 is missing from the configuration file at /etc/apache2/conf.d/lsapi.conf file, add there:
AddHandler application/x-httpd-lsphp .php .php4 .php5 .php53 .php54 .php55 .php56 .php6 .php7 .phtml
Then restart the Apache service with
service httpd restart
The website should now load fine.