Check sn of tractor on id plate,if 720,000/above there are 2 fuseholders/fuses behind dash,one fuse is main power to ign sw and is installed between battery pos(+) and pos(+) terminal on ammeter,if this fuse blown nothing on tractor will work(starter,lights)2nd fuse is for headlights/tail lights,if fuse between battery & ign sw not blown then there is an open circuit between battery terminal on starter sol & ign sw,possible causes:
Battery cable loose on starter sol terminal.
Wire to ign sw loose/broken on sol battery terminal
Ammeter bad or connections on same loose/broken
Ign sw bad.
Loose or bad neg(-)battery connection to eng block/chassis due to rust/dirt.