There are multiple causes but here is one that costs nothing but a bit of time to fix.
Remove all power from the system (Often the battery disconnect will do this)
Cycle the slide out switch like 50-100 times.. Just push and release, Push and release.
Option 2.. if you can open the panel you can check to make sure all 3 wires are attached (one may have come off) and if so remove the CENTER wire and do the above 50 - 100 cycles then re-attach the wire
A guarantee I can not give you .... but the cost is $0.00 so your money is already refunded with a :)
