Number one check that the batteries are connected correctly. Red or black to positive and White to negative. Make sure you didn't miss any wires, look carefully around and under the batteries. After that check the fuse panel and check all the fuses. I'm guessing you have a bunch of 10 and 15 amp fuses and then one or two larger maybe 40 amp fuses. The bigger fuses are your reverse polarity fuses, check them carefully. Make sure all the fuses are good. The best way is with a meter. If no meter then pull them and inspect.