Pedro,
Doesn't seem to be a firewall issue!
If the PCS database copy is working, the PCS can connect to the main callserver.
What you describe is the normal way a PCS works!
Normally the PCS isn't active and has no use of the license.
Only when the CS stops working and the PCS needs to take over, the 30-days limit will count.
Meaning you need to get the main CS working within 30 days.
Most of the times this will not be an issue.....
You don't want to use the PCS for over 30 days