HELP. No start

[Ozruss90]

1990 #1948. Went to take it to cars and coffee last weekend and engine wouldn’t crank over. Jumped in the ‘61 and took it instead. Just assumed it was a flat battery. Put the charger on and checked it a couple of days later. Still no start or crank, thought that was odd so connected a jump starter and still nothing. I have full full dash lights when key is first turned but once turned to the cranking position, dash lights go out and nothing happens. Not even a click from the starter solenoid.
Today l took the panel off under the steering wheel to access the clutch switch to test (wanted to change the footwell globe to an led anyway). Took the connector off the switch and bridged it . Still no cranking. HELP......
When lifting the hood to connect the jump starter, l noticed mice droppings scattered around the engine compartment. Thoroughly checked all visible wiring and nothing chewed but obviously can’t see if any damage under the plenum.
Would like to exhaust all other checks before resorting to pulling the plenum.
Any advise appreciated. Ps. Only done 11k

Cheers from down under 🇦🇺
Russell