I can only suggest first you check your details are complete and correct in Watch app, My Watch, Health, Health details as it needs these to calculate.
and preferably 'Mirror my iphone 'is turned on.
I assume you have been getting activity rings?
If the above does not help then the next activities are procedures for naughty Watches in general.
First force restart the Watch
i.e. press and hold both the side button and Digital Crown for at least 10 seconds, then release both buttons when you see the Apple logo.
Then Force Restart the paired iphone Force restart iPhone – Apple Support which may not be an obvious thing to do.
If that is no help
Unpair and erase your Apple Watch
and then
Set up your Apple Watch
If no better you may want to unpair then set up without restoring the backup.
You may also want to make sure the software on the watch is up to date.
Update your Apple Watch
If you've completed that troubleshooting and the issue is still not resolved, Contact Support.
Click here > Contact - Official Apple Support
or phone numbers
Click here > Contact Apple for support and service - Apple Support