Since version 4.4, a built-in firewall is included in RDPlus Security.
As a general guidance, if Windows Firewall is activated on your server, then you should use it to enforce RDPlus Security rules (default). If you installed another firewall, then you must activate RDPlus Advanced Security built-in firewall.
In order to activate the built-in firewall, go to Settings > Advanced > Product > Use Windows Firewall and set the value to No:
The Unblock after setting allows you to automatically unblock IP addresses after a certain amount of time (in minutes). Default value is 0, disabling this feature: