Fitness Data Not Tracking; Greyed-out Rings

I have 2 series 9 Apple Watches, and the fitness tracking only works intermittently. I thought the issue was because I was using two watches (even though I have done this for years), so I deleted one from my phone two weeks ago, but the issue persists.

The fitness rings are greyed out, and it will not track my heart rate or steps. I have done all of the following on both devices:

1. cleaned and tightened my watch.
2. used different straps
3. restarted both devices (multiple times)
4. unpaired and repaired watches (several times)
5. recalibrated my fitness data

When I unpair and repair it will fix the issue, but only temporarily. Sometimes it works, and other times it refuses to track anything.

I am in some fitness challenges and also track workouts for Weight Watchers, so this is incredibly frustrating.

Because this issue has persisted with two watches, I feel like it isn’t an issue with my watch, but with the app or my phone.