Samsung Galaxy Ring
Issue: Samsung Health shows "Measure your blood oxygen level with your watch"
Fix: In the wearable app Select your ring (if not already selected). Go to : Health Settings -> Sleep. Make sure you have Blood oxygen during sleep enabled. Once you have a nights sleep you should start seeing the data in the health app under blood oxygen.
If you actually have a watch that detects blood oxygen you will need to turn that off. Go to wearable app, select your watch, Go to : Health Settings -> Sleep and disable Blood oxygen during sleep