I am going to list the problems starting from most probable so it could be:
-Your battery since you have not started the car for quite some time your battery could be your problem
-alternator or starter could be your next problem so try hitting your starter with something a couple times as someone turns the ignition and gives it some gas
-Gas could be another reason and hopefully to your luck this is the one so check on this too.
-Electrical problem (which I left for last because if this is the case your going to have fun trying to find out what is the problem) if you get to this case I suggest using a tester. or check your fuse box. You can find one at advance or discount auto parts
Good Luck