Best answer by Airgetlam
Maybe you broke a 5.1system up, and assigned the surrounds and the sub to a new room, and now are trying to add the PLAYBAR? Probably easier to do it the other way around at this point. Create a new room called “Test”, or better yet, hpjust use the room name that the PLAYBAR is in, and re-add the surround speakers and SUB to it, then just rename the room to whatever you want it to be.
I think what you may be running in to is that the pair and SUB are already considered a “complete” room, and another speaker can’t be added.
If I’ve completely misunderstood your issue, let me know