Nuki Opener with Fermex 3311 - wont learn doorbell sound

This is in relation to a new installation. I am installing my Nuki Opener to a Fermax 3311 intercom. My Nuki opener is connected to the Nuki bridge and my phone is connecting via Bluetooth and WIFI so I believe my configuration is OK. When I get to the step “ring the bell to your apartment once, so that Nuki can learn the doorbell signal*”, I do this but after a short time the app responds with “To configure the opener you have to be connect via Bluetooth or Nuki Bridge” As I am connected, I am unable to get past this step. Any help would be appreciated. Thanks in advance.

Hi! This has nothing to do with your connection, it’s the normal behaviour when the ring signal is not recognised right from the opener!

OK thank you, is there a way to ensure the ring signal becomes recognized by opener?