I have a 97 chevy and the only way to start it is to jump the starter relay, not sure if it is the key switch ot the nuetral saftey switch.
Shift the truck to neutral, then try to start it. Thee NSS may be out of adjustment or have a bad contact in the ‘Park’ position.
You can also test the switch…If you are jumping the relay terminals already then you need to probe term 85 or 86…bec one of those is the relay Keyed trigger. While 30 is hot I think and 87 the starter solenoid…or is it the other way round, Im getting foggy at the moment…but ez enough to suss out. 85 and 86 energize the coil of the electromagnet…so one is a ground the other will be the “keyed on”…so see if you get anything probing those terms while you or an assistant turns the key. If not then Busted may have something…bec that neutral switch comes in between the key switch and the relay…so…You’ve now got a bit of homework to do…