Un-Stick a door latch

In the future, you should invest in a better penetrating oil. Guys here will have many opinions on that. Looking at the mechanism from the top- try wiggling the button on the outside door handle. That should tell you which arm on the mechanism is activated and in which direction it wants to go to unlock the door. With that long screwdriver, I was hoping that you could more pressure on it to open it. With a friend applying pressure from the inside was hoping that would be enough. Also be sure that door is not in the locked position. Once again, jiggle the door lock button up and down and be sure the mechanism is unlocked. Sometimes these little things can be a *****. Good luck.