Starter button does absolutely nothing.

So I just yesterday bought a 2008 trx450er and it runs and drives perfect no issues. Today I go to start it up and the battery’s dead, so I go to put the jumper pack on the battery but I put the positive on the negative and the negative on the positive. So I fried a fuse which I replaced and now the starter button does nothing at all even with the battery charged up(battery is brand new) nuetral light is on headlight works all electronics work except for the starter button.