Does the vehicle have a theft system? Are there any trouble codes?
Automatic or manual tranny?

When the starter refuses to run, check for voltage on the black wire with
yellow tracer at the starter solenoid. With the key turned all the way to
crank, that wire should be hot.

If there is a starter relay under the hood or wherever, that is easy to
get at, you can test the starter from there. If you try this, make sure
the tranny is in park or neutral and the e-brake is set. You have to do
the testing while the problem is ongoing.