Ugh. Weird that the app can communicate with the pedals to zero reset them, but that it doesn’t show power / cadence etc.
Taking a complete flyer with this one: have you ever connected anything like a Garmin watch to your SB20? If so, try removing the SB20 from that. My wife records her SB20 rides on her Garmin Fenix, and one time I was experiencing totally wacky behavior that we tracked down to her watch being on in the office (floor above the pain cave) and connecting to the SB20 at the same time I was trying to use it.