Activity, Move, Stand app not working

I have a third generation Apple Watch that I purchased two years ago. The watch had been working perfectly up until two weeks ago. Firstly for a period of about 36 hours the exercise ring was not registering walks, even though I was using the workouts and it was recording the workouts. At that stage both the Move and Stand rings were working ok. Now, the Exercise ring is recording properly but the Stand ring has me standing daily from midnight, so that by 7pm I have apparently been standing for 20 hours and also the Move ring is not registering any of the exercise I am taking which has amounted to nearly 10km most days. I have tried all of the suggestions given for the Activity app not working on this forum - I have switched off both my iPhone and watch and restarted the iPhone first. I have checked the calibration on the watch and activity app, I have reset the watch to factory settings and re-paired the watch to the phone, but still nothing not working. So far today - according to the watch, it has (correctly) registered that I have clocked up 75 minutes of exercise, 10,338 steps, 7.6km - (incorrectly) 14 hours of standing and despite all the exercise above, moved just 29 calories. Any further suggestions of what to try would be appreciated. Thank you.