Trouble adding controller

Hello!

For whatever reason I am unable to pair an Android tablet as a second room controller to an existing Zoom Room.

Whenever I log into  this device (with the main Zoom Admin Account) it does NOT present me with a list of Zoom Rooms but just a single room "Firstname Lastname 1" which never existed. I also dont have any option to add a pairing code or anything else.
The only thing available is to TEMPORARY add the tablet as a controller but this is in the context of the logged in USER but not the room. You know, where the admin users icon is shown on the big screen as a temp. controller.
SO, how do I add this tablet permanently as a second controller?

Could it be, that there are some leftovers from the fact, that there was Zoom Client installed on this very device?
I uninstalled it weeks ago but maybe zoom room controller still finds something...

Thanks for any gudidance.
HST