If your pattern of daily activity has not changed significantly and you would normally expect to have achieved Exercise credit, it may otherwise help to close all open apps and restart both your iPhone and your watch.
On your iPhone, close all open apps:
- Double-press the Home button, then swipe up on each of the app previews to close them.
Restart both your iPhone and your watch:
- Turn both devices off together, then restart your iPhone first;
- To turn your watch off: press and hold the side button until you see the Power Off slider; drag it to turn off;
- To turn it on: press and hold the side button until you see the Apple logo.
If the issue then persists, next try unpairing and re-pairing your watch:
- The Watch app on your iPhone takes a backup of your watch automatically when unpairing via the app.
- Choose to Restore from Backup when offered the option during set up. Most data and settings will be restored, with some exceptions (eg Apple Pay cards, passcode).
- Unpair your Apple Watch and iPhone - Apple Support
- Set up your Apple Watch - Apple Support