Why won't my Mitsubishi start?

I accidentally put the battery in backwards, swapped
everything back around and checked every fuse both in
passenger and under hood. The only blown fuse was the
hundred amp under the hood that goes to the alternator.
Replaced that and all the electrical systems have power
and work fine, however when I turn the key I'm unable to
hear if it's priming the engine to start, engine attempts to
turn over fine but nothing actually ignites.