Attach a remote start switch to terminal "s" and the battery connection on the starter/solenoid; or jumper the two. The remote switch is much safer and not all that expensive at an auto parts jobber or parts store. If the starter turns the engine when the remote switch or jumper is used, then you know the starter is ok and the problem is either the key switch or in the wiring system and/or bulkhead connector. Use a process of elimination one step at a time.