So many of these 'tractor won't start' threads!
First things, first, eliminate the common failed components:
Battery and Starter.
Take a jumper cable and hook it up to the positive on the battery and touch the other end against the main starter terminal. If it turns over at speed, both are good. If not, you can test the starter itself from a known good battery like from a car or truck. If it turns over, your battery is shot. If not, your starter is shot.
Now that you know it's not the Battery or Starter...
Now start checking other things like fuses, relays, solenoids, safety switches. Each can be checked with a meter, bypassed, jumped, whatever. Get a schematic for your tractor and hunt them all down, or just follow the lines back to their relative points if you can access them all.
At the end of the day, totally unworking electronic stuff is easy to diagnose, a pain to do it some times, but easy. HARD electrical issues are the darned intermittent ones!
We need a sticky with the "I can't get the tractor to turn over..." common diagnostics path to point at...