If non of the usual suspects for a no start check out go after the anti Theft. First I would check the ignition switch. Remove the clam shells around the steering Colom, pop the connector off the ignition switch and then use a bit of wire to bridge the power to the car, and then trigger the start. If it fires up it was the switch.
If you still have nothing key the car on and then use a screw driver to bridge the main power on starter to the solenoid. If that starts it Id be looking at a relay or the Anti Theft.
The above right is correct about that generation of car. They weren’t the most methodically thought out electrical system in the body. Super simple but had issues due to placement of connections and corrosion. Check for clean grounding or any broken wires.
In Mk3 cars, particularly ones produced in Mexico they were known for a bad window seal that allowed water to leak down onto the fuse block area…..Handy.