Without seeing it I cannot give you an accurate diagnosis of what is wrong
But here are one or 2 things to check
1) Does it open with And without the key?
2) is the safety button/lever inside pushed down? (try pulling and pushing it) then opening the door from inside
2a) open the door then pull the lever button
does that work?
On well worn doors the knob on the safety lever comes partially loose thus not pulling the opening mechanism
fully undone no harm in checking for this
3) squirt some penetrating oil on the lock itself may be a tiny hole that allows you to squirt into the internal mechanism also you may? find a tiny lever which is a safety feature fitted on some doors to stop it being opened from inside.But I've never seen nor worked on a Dodge as I am Uk based

It will be indicated in the vehicle Handbook if they are fitted? Perhaps under Security?

Last Idea. Could the lock on the door be a deadlock? Perhaps the mech has been set by accident? try rotating the key in the
wrong direction if the deadlock is set in the
ON position then twisting the key "
might" undo it to the
OFF position?

Remember the lever handle I mentioned earlier?
If you have somebody inside they may see or hear this lever moving? When you open with the key? then all being well the door will open normally

Ther may be a sentence in the handbook that refers to this?
Have no handbook then you have 2 options 1) go to the public library and see if they have a Haynes manual for the van and make a photocopy of the door page or 2) Go to the Dodge (Chrysler?) Main Dealer and ask for a photocopied page of the handbook which deals with doorlocks. They may even loan you the book? for a deposit?
