Is the battery fully charged & passing a load test? All fuses ok? If the starter works (when bench tested, I assume), but not on the tractor, are you getting power to the solenoid when you turn the key? Good ground? Will she crank when you jump the solenoid on the tractor? Have you checked the cables & ground connections for resistance? I had to replace my ground cable, clean up the frame connections & replaced the crappy battery connectors with marine type terminals to get a decent connection on the posts. I've seen some posts of bad LS key switches. My LS was flooded by Hurricane Ian, she started once after I recharged the battery, but wouldn't start a second time, when I pulled the starter to test, saw the bendix and shaft were rusted solid & had to replace the starter. Depending on how long she's been sitting, I'd start with battery condition go to cable/connection cleanliness then starter internals (rust) in my approach to diagnosing. A good set of jumper cables run directly from the battery to the starter hot lug and an ear of the starter is a quick/easy way to see if the cables/connections on the tractor are your issue. Don't overlook fuses either ... low volts can drive amps up & blow fuses. When you get it figured out & putting together use lots of dielectric grease to minimize future problems.
