I had a similar problem with a 1986 244GL RR door. Lock knob up and down just fine, manually or electrically, but the door remained locked. Here's what I did:

I have a 1984 244GL parts car on which all doors open OK. I pulled off the RR trim panel to look over the linkage. If you don't have another similar car, use your RR door. It is so much better to use the same door that it would be worth it to "borrow" a friend's car for a model (no damage done) or do the long coat hanger hook forming steps with a junk yard LR door.

In my case I saw that the long rod between the lock knob and the lock mechanism was quite bent - improper use of a "slim jim". Therefore when the lock knob was up, the mechamism part had not far moved enough to let the door open.

In your case, since it just happened, it's likely that a place where two linkage parts connect has become disconnected. Due to rust or something else.

Now the meat:

There is a pin that sticks into the inside of the door from the mechanism that is on the outside, the part on the rear edge of the door that holds the moving lock piece. That's the piece that rotates to "capture" the lock bar on the door frame.

Working with the "model" car:
1) With the door open and the lock piece manually moved to "lock" position, find that pin and move it (hard pull) upwards, which will cause the lock piece to snap to the unlock position. That's how to tell you are moving the correct pin. The pin is not obvious, it's behind some other linkage.

2) With the window rolled down, and looking into the door cavity, I worked on a long piece of coat hanger wire to form a long hook with which, standing outside the door, I could reach down into the door through the rolled-down window slot, find that pin and pull it upwards.

In fact, to pull the pin as in 1) above, I formed the hook and went in through where the trim panel fits and worked the wire to get it to grip the pin and pull. Then went to step 2).

3) Took an hour or so to get the wire into a shape that worked. You will need two pairs of pliers, maybe one a pair of Vise-Grips, and maybe work gloves.

4) Then, after dark and using a flashlight (held by a helper, on a headband or in your teeth) to see down inside the perma-locked door, I fitted that wire on the pin and pulled. Most of the time was spent getting the hook onto the pin.

Once the pin was found and pulled hard, the door opened. The job took maybe a half hour. Doing it after dark is important. Daylight will make it more difficult to see into the dark door insides.

Once it is open, pull off the trim panel before you close it. That way you can close and lock it and re-open it when needed.

Good Luck,

Bob

:>)