2012 sportsman 550 fan relay

i have a 2012 sportsman 550 that I cannot get the fan to run on. I’ve tested fuses pulled the temp sensor plug checked the circuit breaker swapped relays around and even replaced the relay. Tonight I took the fuse/relay holder off the machine and with a test light probed the back side of fuses and relays. When I ground one terminal of the relay the fan came on. Any ideas of what is the problem.