If all Electrical functions appear normal, try:

On the starter solenoid there are two terminals:

- One connects the heavy battery cable to a threaded lug. Don't mess with that one for now. And if you do, disconnect the battery first.

- Next to the large solenoid terminal is a small one-spade terminal / connector and a single thin primary wire. This is the feed wire to the solenoid that triggers the starter circuit. The spade connectors may be corroded and not allowing a connection, after sitting for so long.

Disconnect the spade terminal and clean the male and female contacts. Electronic spray cleaner and then dielectric grease helps, if available.

Reattach the spade terminal and try starting again.