Remove your instrument panel from the dash and pull any fuse. Turn the key to RUN position and check the fuse for power. The key switch supplies power to one side of all fuses when you turn it to RUN. If you can keep the meter attached while turning the key on/off, you should see power on/off to the fuse bus. If you don't see any power at the fuses, then the problem has to be in the ignition switch.
Glow plug power is determined by the glow plug timer. If it is faulty, you may never see the glow plug power light, but you should see power to everything else. You didn't say it, but I'm guessing your tractor won't start either. Try finding power at the fuses. If you have power at the key switch output side and none at the fuses, then you have a broken wire. According to my schematic, the wire from the switch to the fuses should be a big orange 10 ga wire.