Which solenoid post did you cross,,if it was the two large ones then the starter will only motor (run but not engage flywheel) as you were bypassing the solenoid.you must cross the top large stud and the small one next to engine block (assuming this is a chevrolet engine).
As for the extra post you mentioned on solenoid,,it is not used, it is a points bypass from a bygone era.I dont know why there still on replacement solenoids but they are
From reading your post I feel like you are not getting any key switch voltage to the solenoid.someone mentioned to check starter relay and fuses,this is very sound advice.also try moving gear shift from park to neutral you may have a neutral start switch on trans that has gone south.
Also while crossing starter over I would highly recommend having someone in drivers seat holding brake ,because coach will start and if it inadvertanly left in gear it will run over you