The PHP developers deprecated mcrypt in version 7.1, and removed support in version 7.2.
Here's how we can install Mcrypt PHP extension on a cPanel server.
Just by using the following commands
yum install libmcrypt
yum install libmcrypt-devel
/opt/cpanel/ea-php72/root/usr/bin/pecl install channel://pecl.php.net/mcrypt-1.0.1
As always if you need help, one of our sysadmins is stadning by to better assist you.