If the Fitness app or Health app is restricted due to battery optimisation, background app refresh being disabled, or Low Power Mode being enabled, the ring graphic may experience stalling.
To resolve this issue, forcefully close the Fitness app and then reopen it. The rings should be redrawn correctly.
Alternatively, restart both your iPhone and Apple Watch, as this often clears sync glitches.
Verify that the Fitness Tracking and Health apps are enabled on your iPhone by navigating to Settings > Privacy & Security > Motion & Fitness.
Ensure that background app refresh is enabled on your iPhone by navigating to Settings > General > Background App Refresh.