This is a common issue with the Backtrack feature on Apple Watch Ultra. Here are some steps to resolve it:
1. Enable Precise Location for the Compass app: On your iPhone, go to Settings > Privacy & Security > Location Services > Compass and make sure it's set to "While Using" AND that "Precise Location" is toggled ON.
2. Enable Location for the Backtrack feature specifically: On your Apple Watch, open the Settings app > Privacy > Location Services, then find the Compass app and enable precise location there as well.
3. Check watchOS is up to date: Make sure your Apple Watch Ultra is running the latest version of watchOS. Go to Watch app on iPhone > General > Software Update.
4. Reset Location & Privacy: On your iPhone, go to Settings > General > Transfer or Reset iPhone > Reset > Reset Location & Privacy. Note this will reset all location permissions and you'll need to re-grant them.
5. Restart both devices: A simple restart of both your iPhone and Apple Watch can sometimes resolve Backtrack not detecting precise location.
6. Ensure GPS is working: Take your Apple Watch Ultra outdoors with a clear view of the sky and allow it a moment to acquire GPS signal before starting Backtrack.
Hope this gets your Backtrack feature working!