If you hear a click when you press start, the start/stop switch is fine.
First, make sure that the black cable going from the negative terminal of the battery is fastened securely to the batter terminal and to the back end of the starter.
If you have a voltmeter/DMM, measure the resistance from the negative battery terminal to the engine block.
After all that checks out, I would open up the ebox, disconnect the red cable going to the starter from the relay, and briefly touch that cable directly to the positive terminal of the battery. If the starter doesn't turn that way, you have a bad starter.
How would a starter go bad randomly though..... all it did was sit for maybe a month or two with out being started... plus it is an 2007 SJ rather new! I hope thats not the case!