Replacing solinoid
Before replacing anything, check for failed engine ground. If using jumper cables, use only the black cable, do not connect the red cable. Connect one end to the battery negative terminal and the other end to anywhere on the engine where you can find clean metal, even if you have to sand it clean. The try starting. If it starts, install permanent new secondary ground from negative battery terminal to an engine bolt. If no start, then remove starter with solenoid attached and have it tested at an auto parts supply store. If it fails the test, replace it. If passes the test, reinstall, then set about cleaning all electrical connections, that is disconnecting, sanding or polishing, applying a thin layer of dielectric grease and reassemble and tighten. Do this one by one with battery terminals disconnected, tracing from the solenoid, back to starter, back to ignition switch to master fuse block and back to battery positive terminal and on negative side from batter to ground. If you have an oscillating tool with a miniature sandpaper holder, it works wonderful for polishing electrical connections. If all connections clean and tight and still no start, try bridging the solenoid to eliminate the key switch and see if it properly operates. If so, then the key switch has just been identified as the culprit.