I have a 1950 Chevy 1/2 Ton PU. I bout a new lock key assempbly from Chevy Duty and installed it on the passenger's side. I insert the key and turn the lock. It turns but does not lock the door. Any suggestions?

I am pretty sure I have the square lock dowel inserted into the door latch mechanism. The only thing I can think of that could be a problem is that before installing, I did not ensure the square lock dowel was not rotated to a position that when you turn the key, it rotates enough to unlock the door.