Do a voltage drop test using a multimeter.
First, check the fuse(s).
Then, make sure power is getting to the small wire that goes to the solenoid from the ignition switch when you turn the key to crank.
Then, check for loose wires at ignition and solenoid.
Last, do the voltage drop test.
If it was working fine last time you used it, more than likely, the battery cables and connections need to be cleaned. Could be the solenoid finally bought the farm. Each can be tested before replacing.
Me and I think Hal have the same tractor.