Hello,
Relays rarely fail. Have you checked for 12v across the coil? You could apply 12v from a battery or power supply just to prove that the relay clicks over.
If the relay has failed, it's a pretty standard item and it shouldn't be hard to find one (I probably have some somewhere in the shack).
Let me know how you get on with your tests.
King regards,
Chris. G0VOE, Somerset.