I had the same issue after a power outage. The doorbell was not ringing on any of the intercom devices. Power cycling the control unit did not help.
A clue was that the intercom list showed the Doorstation (doorbell interface) as disabled, while all other intercoms (my connected iOS App and the touchscreens) were reachable.
I checked the IP address of each intercom and all were correct. The Doorstation was listed with the correct IP address. Once I knew the IP address and the port of the Doorstation, I unplugged the port to power cycle the Doorstation. Once it came back online, the Doorstation registered on the intercom list and the doorbell worked.
My theory to this issue is that the Doorstation needs to register online after the Control Unit has successfully booted, otherwise the Doorstation may not connect properly.
