Try disconnecting and reconnecting every connection in the system. Sometimes corrosion
can build-up on the contacts causing enough resistance to introduce connectivity issues. I've seen this occur on circuit boards connected to motherboards, spade style fuses
, even pin style light bulbs.
I would unplug and re-plug several times. The process can scrape off the corrosion
and leave a good contact. It may do nothing, but it is where I always start and it fixes things a surprising number of times.
(Kind of like when a small electric motor
stops working....Step #1, tap it with a screwdriver handle a few times).