Tap IP Cannot connect to Zoom Rooms

We have a small room solution with Rally Bar Huddle and Tap IP running on the same LAN (wired). Our Rally Bar Huddle is successfully connected to Zoom Rooms and can start a call. However, our Tap IP doesn't want to connect to Zoom Rooms - afaik in this case it should connect to the controller, meaning the Rally Bar Huddle. The local IP is correct, i.e. Rally Bar Huddle is at 192.168.8.35 and that's where the Tap IP is trying to connect, but the message we always get is "Cannot connect to Zoom Rooms".
We might be doing something wrong but I really cannot figure out what, so any help will be appreciated.