I know this is an old thread but I was searching because I ran into similar issue. I have a hub, and it’s assigned a room, however I could not add a z-wave device with the same error you ran into.
I thought that hiding the hub was a good idea … it’s there in the background doing it’s thing - however - when the hub is hidden it will throw that same error. Just sharing here as I spent the last 10-15 minutes trying to figure out what was going on. Hopefully someone else will find this useful 