Welcome to the forum! Wish it was under better circumstances.
Does the tractor crank over but won't start or it doesn't do anything when you turn the key?
If it does nothing when turning the key:
Can you tell if you're getting voltage to the key? Do any lights glow? If no voltage or lights, it could be wiring to the ignition or the ignition itself.
Can you check the voltage to the starter solenoid with the key on? No or low voltage to the solenoid could be wiring issue there or a safety switch has gone bad. (I'm assuming you have everything in the "safe start" setup like the PTO off, possible safety switch at range selector and clutch).
If you have everything in its safety mode and it's safe to do so, you could run a jumper from the battery to the starter. If it starts, it's probably a bad safety switch or ignition.