will not turn over?

Hello,

Have you checked battery condition and terminals?

I would suggest to first check that battery is fully charged and that the terminals
clean and secure.

see some reading material:
https://www.2carpros.com/articles/everything-goes-dead-when-engine-is-cranked
and
https://www.2carpros.com/articles/how-a-starter-and-solenoid-works

Cheers, Boris

everything is in working order, put a multimeter on battery, alternator, coils, starter, all reading 12+
everything goes it just won't grab and commit.

Hello,

So the engine is not cranking over? Or is engine cranking but will not fire?

You have 12V at starter solenoid, have you checked if you also get 12V at the starter solenoid exciter wire when cranking the engine?

See diagram below, for an 1989 Nissan Hardbody VG30.
The 12V from ignition switch is routed through the starter interlock rely to the starter solenoid.
The starter solenoid is grounded via the clutch switch.

Cheers, Boris