Wattbike -> Apple TV No Signal

When I try to connect my Wattbike Atom to a new Apple TV 4k, it finds the bike fine on Bluetooth but then says ‘No Signal’ after it’s connected. Never had an issue on iPad or iPhone. I have tried updating the Apple TV firmware and Wattbike firmware (I don’t think it even needed an update but went to Beta and then back again to see if that worked).

Very frustrating. Any ideas?