I had the same problem… and later on when I had some funky behavior (devices dropping offline), I remembered some advice one of the power users here suggested: There may be corruption or a sync problem with the device tables in my hub < – > cloud.
The fix was really simple: Unplug your hub from power (remove batteries if they exist) for at least an hour. In my case I just did it overnight. The cloud version is cached but only for a (few?) hours. When you plug the hub back in, they are forced to resync.
Worked like a champ last night - and I remember seeing your post so wanted to mention that as a possibility. I use Whole House Fan also - that is our “central air” system!