Make sure you have sufficient battery, likely from what you're indicating, but still; and that the connections are good.
Make sure starter is properly wired/connected.
Check to see if you get a 12v+ signal to the starter trigger wire when key is turned to start position.
Check that the clutch pedal interlock switch is functioning properly, or remove it from the circuit. I don't remember if that is a normally closed or normally open switch, but you'll want to simulate the condition you should have when the pedal is depressed.
Bad ignition switch, bad starter, bad battery, bad clutch pedal interlock switch, bad wiring to starter, or perhaps alarm/ignition interlock are the things that could cause nothing to happen as you describe.
Start validating each to rule them out. Hope this helps.
Check your Bentley manual for more in depth tests for those individual items.