Me and 2 friends are trying to have a multiway conversation between 2 Dena 20S and 1 Interphone F5MC.

Hi have followed the guide down to the smallest detail but in the end, we end up with 2way connection with one "master" which controls who the master wants to talk to, but no multiway.

What are we doing wrong ?

We used this guide: https://m.youtube.com/watch?v=9v8flrla0VI

And both methods