Hi ishekia,
Thank you for using Apple Support Communities.
I see that you’re having an issue with the activity on your Apple Watch. The exercise ring stops working at times. If you have not yet done so, update your iPhone and Apple Watch to the latest compatible software versions, starting with your iPhone. It is a good practice to back up your iPhone before updating.
Here’s How to back up your iPhone, iPad, and iPod touch - Apple Support
Here’s how to: Update your iPhone, iPad, or iPod touch - Apple Support
Here’s how to Update your Apple Watch - Apple Support
If everything is updated and the issue remains, I would recommend restarting your devices.
Restart your iPhone, iPad, or iPod touch - Apple Support
How to restart your Apple Watch - Apple Support
Also, this article has the steps to Get the most accurate measurements using your Apple Watch – Apple Support
Hope that helps.
Best Wishes!