I have had this problem happen an a few cars that come into my shop. It’s never fun but can be interesting. The door latch assembly is at the rear part of the door about half ways up as it is on most cars. There are 2 rods that run from the interior handle and 2 rods that run from the exterior handle/lock cylinder assembly. These rods are retained in place by small sometimes fragile metal or plastic clips that sometimes break and let a rod come loose. I have seen them stuck from corrosion also. If you can put the window all the way down take a small bright flashlight and look down in the gap where the window is. You can usually see the latch assembly on the inside of the door. Try operating the exterior key lock or the interior lock and you may see why it is not working. A rod can be fashioned with a small hook on the end to possibly pull on the lock mechanism to release it. I hope this helps a bit.