[Str8Razr]

BCGreen, not saying you did this, but my buddy put his charger on backwards and it killed the battery. It's also possible that a fuse blew in the battery tender. Now is the perfect time to get a voltmeter if you don't have one already and check both that the battery and battery tender is working. First check the battery not connected to the charger. It should be above 12V. If below, then there is a charging issue/possible bad battery. If the battery is showing above 12V, connect the charger and keep your eye on the meter. If it is working, the voltage should start slowly rising. If everything looks OK and the car won't start, then someone else is going to have to chime in on fault elsewhere, like the starter.