Hi
The following steps may help (check after each):
If you have not yet done so, then update both your iPhone and Apple Watch to the latest software, starting with your iPhone (make a backup first):
If you are sharing an Apple ID with another user, then stop doing so.
- For Activity tracking and reporting and various other features and services to work as intended, each person should each have a separate Apple ID and be signed in accordingly on their own devices.
On your iPhone, go to: Settings > Privacy > Location Services:
- Check that Location Services (the main setting at the top) is turned on.
- In the list of apps beneath, check that Apple Watch Workout is set to While Using.
- Also enable options under System Services (via the link at the bottom of the page) including Motion Calibration & Distance, Setting Time Zone, Wi-Fi Networking and Mobile Network Search.
Check your personal information:
- Activity-related estimations depend, in part, on your personal information.
- To check that this has been entered accurately - and to keep it updated over time:
- On your iPhone, in the Watch app, go to: My Watch (tab) > Health > Edit - tap and adjust items, then tap on Done.
If you have ever previously used any third-party fitness tracking, sleep tracking and/or heart rate monitoring apps:
- Check the developers' support resources and/or contact the developers to check for any known issues affecting how data is shared to the Health app on your iPhone.
- Check whether there is an active or paused session within any of them.
- If there is, then end that session from within that app on your Apple Watch.
- If in doubt, it may help to remove any such third-party apps from your Apple Watch, at least temporarily.
Close certain apps and restart both your iPhone and your Apple Watch (normally):
- Close the Watch app, Activity app and Health app (if open) on your iPhone:
- Double-click the Home button, then swipe up on each app preview to close the apps.
- Turn both devices off together, then restart your iPhone first:
Reset your existing calibration data and recalibrate your Apple Watch:
- Calibration can improve the accuracy of estimations made by Activity app and Workout app.
- More information and instructions are available via the link below:
Be sure to allow the arm on which you are wearing your Apple Watch to swing naturally during general daily wear, during relevant workout activities and also during calibration.
If the issue persists, then it may help to unpair and re-pair your Apple Watch:
If the issue still persists, then I suggest that you contact Apple Support (remote diagnostics and/or mail-in service may be available, if required), make a Genius Bar reservation or visit an Apple Authorised Service Provider for assistance: