Glad you got it sussed. Applying voltage to the fan switch connector shouldn’t do anything, you just need to bridge those to pins together, that is what operates the relay
definitely sounds like you had a bad connection somewhere though. When fitting the new fan loom it is advised by specialists to fit the relay part behind the battery so it doesn’t get wet, I made the mistake of putting them next to the ignition amplifier on the inner wing and my fans wouldn’t go off after washing the car.
Thats where I fixed mine, need to re think this then.