Hello and welcome to JustAnswer!
I see that your question has been up for an extended time without a response and although this vehicle isn't in my area of greatest expertise I would like to try to help.
Are you unable to physically turn the key to the unlock position but you are able to turn it to lock? If you're able to insert the key and turn it to the lock position then you can rule out the key itself or a lock cylinder issue.
If you can turn the key to lock but not unlock, or the key will physically turn but won't unlock the doors then you have a latch or linkage problem. What you would need to do is remove the door panels and make sure the linkage between the lock cylinder and latch is intact. If the linkage is bent then it will prevent unlocking or something foreign is blocking it from moving fully to the unlock position then you won't be able to unlock the door.
If the linkage looks ok and the key turns fully in the lock cylinder in the unlock direction then the problem will be the door latches themselves.