I don't have your model, but both of my trailers have/had a fuse feeding the propane detector. It was an inline fuseholder in the same general vicinity as the
12V distribution panel. You could also look behind the detector at the wiring.
Also, on both of my trailers, the detector was always on, i.e. i was not affected by the STORE/USE (Battery Disconnect) switch.
As an alternative, maybe the detector has failed. Simple test - get a voltmeter and check the power at the detector.
Al