Reset Sync Data' on watch not responding

When you tap on reset sync data you can't actually see anything happening because this happens in the background,it is doing it's job though.

Check your personal details are correct in your health app profile.

Make sure the watch band is snug but not too tight.

Don't wear the watch on top of any tattoos.(Very important)

Check that the 2 side buttons aren't being accidently pressed by your hand or a sleeve

On your iPhone, go to Settings, then tap on Privacy and then select Location Services option and ensure that it is enabled.

On the Location Services section, tap on System Services and then toggle the Motion Calibration & Distance option to enable it.

Then go back to the Home Screen of your iPhone and launch the Watch app.

Then,tap on My Watch option, then tap on Privacy and toggle the Heart Rate option to enable it.

Go back to My Watch section, then tap on Passcode, and toggle the Wrist Detection option to enable it.

Finally, go back to My Watch section, then tap on Workout, and make sure Power Saving mode is disabled. If enabled, toggle the button to turn it off.

Your problem maybe caused by something else.