Watch - 0 Calories During Workout

Otherwise, the following steps may help (check after each):

Restart both your iPhone and your watch:

• Close the Watch app and, if they are open, the Activity and Health apps on your iPhone:
  • Double-click the Home button, then swipe up on each app preview to close it.
• Turn both devices off together, then restart your iPhone first:
  • Restart your iPhone, iPad, or iPod touch - Apple Support
  • Restart your Apple Watch - Apple Support

Try this sequence of steps:

• On your iPhone, in the Watch app, go to: My Watch > Privacy > Motion & Fitness - turn Fitness Tracking off.
• Restart both devices by turning both off together, then restarting your iPhone first.
• Return to the Fitness Tracking setting and re-enable it.

Unpair and re-pair your watch.

• The Watch app on your iPhone takes a backup of your watch 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

Hi

The following steps may help:

Check that you have set up the Activity app on your watch:

• When viewing the time on your watch face, tap on the Activity rings icon / complication, or;
• Go the Home screen (via a single press of the Digital Crown) and tap on the Activity app icon (coloured rings).
• To get started, you will need to enter some personal information.

Check that Wrist Detection is turned on and that, if passcode is enabled, you are unlocking your watch after placing it on your wrist

• On your iPhone, in the Watch app, go to: My Watch (tab) > General > Wrist Detection - turn on.

On your iPhone, go to: Settings > Privacy > Motion & Fitness - check that both Fitness Tracking and Health are enabled.

On your iPhone, in the Watch app, go to: My Watch > Privacy > Motion & Fitness - turn on Fitness Tracking and Heart Rate.

Check that you are wearing your watch sufficiently snugly on the top of your wrist (if it is worn too loosely, your watch may believe that it has been removed from your wrist).

• Your heart rate. What it means, and where on Apple Watch you’ll find it. - Apple Support
• Wrist Detection can be affected by temporary or permanent skin changes, such as by some wrist tattoos.

Check that your personal information is accurate:

• On your iPhone, in the Watch app, go to: My Watch > Health > Edit - tap and adjust items, then tap on Done.

Calibrating your watch improves the accuracy of various activity-related estimations. Instructions for how to calibrate your watch are available via the support article linked below.

More information:

Use the Activity app on your Apple Watch - Apple Support

Calibrating your Apple Watch for improved Workout and Activity accuracy - Apple Support

Use the Workout app on your Apple Watch - Apple Support