Often times on C-4's, owners encountered the No-Start and we would see that there were two sets of floormats, which interfered with a full clutch depression.
Simple, but saw it over a dozen times.
Next step is the VATS. Clean the key; try again, then as Thomas correctly suggested try another key. I have a new tested spare secreted within the car just for such fun days.
The FSM details a very correct diagnosis procedure.
I would rule out the simple things first, but the no dim on turn to start, APPEARS to point to VATS or Clutch Switch, however I would also confirm that there is no deflection , even a minor one of the voltage needle as the key is turned.
Once you see the small gauge of the white wires from the ignition switch running down the column to the module you will understand how easily they can be pinched and fail to accurately convey the needed resistance value.
Bypassing the clutch switch to TEST would then be the next step, although I am not an advocate of permanent bypass. While you or I may never forget to depress the clutch and ensure you are in neutral out of habit, some one else who might move the car may not have the same religion, so if it tests bad, replacing it is the best path. The 90-92 years are very prone to such failures.
If the switch bypass fails, then trace that purple wire as best you can to make sure it is not pinched somewhere.
If still a no go, search for a starter and plan on the plenum pull, but first as said earlier review and perform the diag procedure in the manual.
Keep us posted on your progress.
Marty