1998 Plymouth Voyager Can't get it to start

I lost my key fob and because my driver's side door lock was punched from someone trying to break in I was unlocking the car from the back hatch. Then one day the automatic door lock stuck and was bussing all day. So I undid the battery cable. Then I found out my battery was bad so I replaced it. I then tried replacing the battery cable but could not figure that out so just put it back on. I have tried to reset the computer by taking off the cables and putting them back on and the car lights work, radio works so I know the car is getting power but no starting. I have tried turning the key off and on as several others have suggested to reset the computer, I have had a mechanic run a dianostic on the computer and he siad all checked out. What can I do now?