Door lock vacuum is one of the yellow lines in the engine bay. There's a few vacuum threads w/ diagrams running around. A gauge is helpful, but a Mity-Vac (or equivalent) is pretty much essential at some point in maintaining and testing individual elements.

If you're willing to risk being locked in, you can try depressing the driver's door lock with the door closed. It should pull the others closed if there's vacuum. You may want to try this with the door open and the latch tripped to the "closed" position, though.

Lock issues are a known problem with replacement of cylinders resulting in mismatched sets. Maybe try a different key or try a different door. Odds are your ignition cylinder has been replaced and the door/engine keys don't match.