Master switch will lock all doors but will not unlock them. I've installed a new master lock switch, new 40 amp fuse behind passenger kick panel but problem persists.
Any suggestions?

 

Check the wire harness in the door jamb. Your car is fairly aged and the wires could have become damaged through all the opening and shutting of the door.

 

You can look for a similar issue I had on this forum. The right rear door window had open and close issues as I remember. At the end figured out as said above it was the door jamb harness from years of opening and closing. This door was where the baby car seat was and open and closed a lot. Soldered and reinstalled.