05 T&C doors won't lock

Hi there,
We have inherited an 05 T&C and up until today, there has been no problems. The doors won't lock now either by using the remote or by pressing the door lock switch. The doors will unlock with the remote and the switch. I have lubricated the door lock mechanism although this did not help. When pressing "lock" there is no sound from the door, however, I can hear the doors unlocking (if that makes sense).

Any ideas?
Thanks,
-Mark

Any thoughts?

Ok one more try.

I took the door panel off and notice there are only two wires going to the door lock/unlock switch. The switch works when I push up (unlock). I get nothing when I push down (lock). Pushing lock on the remote does nothing. What kind of troubleshooting can I do with the door panel off? check continuity of the wires? voltage?
please help.

Ok one more try.

I took the door panel off and notice there are only two wires going to the door lock/unlock switch. The switch works when I push up (unlock). I get nothing when I push down (lock). Pushing lock on the remote does nothing. What kind of troubleshooting can I do with the door panel off? check continuity of the wires? voltage?
please help.