Nuki Opener Ring not working

I connected the nuki Opener with the BPT E/220. Please find attached the wiring for your reference.

The Open Door works. The Ring to Open doesn’t work and I don’t get notification when someone rings. I called the BPT support and told me that the slot 4 (RING) doesn’t give electric current (12V) like other intercoms, it works with audio signal. Is there a way to get the Ring working with the audio signal? Do I need a different set up?

Have you a seperat bell, or comes the ring Sound from the intercom itself!?

It comes from the intercom. From the BTU they told me that slot 4 (RING) doesn’t give electric current but audio signal.

This means it gives not enough current to trigger the opener. You would need something, what amplifiers the current to a value high enough to trigger the opener, when someone rings.