Atomicorp ModSecurity Rules key for Plesk 12 has been installed.
While trying to enable
Atomicorp ModSecurity Rules feature under Tools and Settings > Web Application Firewall, a username and password request appears.
Wrong rule set selected.
Plesk has an opportunity to use Atomic Professional ModSecurity rule set as well as Atomic ModSecurity rule set (subscription).
Atomic ModSecurity rule set (subscription) should be selected when it is purchased at https://atomicorp.com/ directly.
In case of using additional Plesk License key, Atomic Professional ModSecurity rule set should be selected.