You did remove the bottom pins and also the springs as well didnt you?
Check you can account for all the springs first off,
Otherwise you should be able to put the key in and turn it unless im missing somthing?
If youve put the pin back in the wrong place then you can cut a new key with that cut in the right spacing to open the lock, alternitively only push the key in so far that the cut is in the right place for that pin,
Otherwise only lift the pin up a small amount if its a low cut,
Unless somthing is jamming the lock i cant see what the issue is with only one pin in it
Please elaborate as im sure i must have missed somthing,