Hi there
Please try this
Enable Precise Location for Clock: On your iPhone, go to Settings > Privacy & Security > Location Services, tap on Clock, and make sure it is set to While Using the App with Precise Location turned ON.
Check Apple Watch Faces Permission: In the same Location Services menu on your iPhone, scroll down to find Apple Watch Faces (or System Services if applicable) and ensure access is allowed.
Check Weather App Settings: The solar and sunrise data often relies on the Weather app's location access. Verify your default Weather app has Always or While Using permission with precise location enabled.
Restart Both Devices: Turn off both your Apple Watch and your paired iPhone, then turn them back on to force a refresh of the location cache.
Re-add the Watch Face: Delete the Solar watch face from your Apple Watch via the Watch app on your iPhone, and add it back fresh.