Auto door locks

I've had my '92 Roadmaster wagon for about 2 months now and still can't get over what a great car it is. I love it!
When I first got the car, when you unlocked the driver's door with the key, all the doors would unlock, you could hear the actuators opening.
A couple weeks ago this function stopped. Now I have to push the unlock button on the driver's door panel. The car has RPO AU0 so I guess it had remote locks originally,but it didn't come with fobs. Auto lock putting it in drive and unlock in park still works.
Is there a way to reset this or has something failed? I've searched the owner's manual and it says nothing about auto unlock.
Also, if I buy roadmaster fobs off ebay, are sedan and wagon the same? Some show a trunk opening pic, some a hatch and some just say "rear".
I can program these myself?

The fobs should have the same number with a T at the end vs. the receiver having an R at the end. I have seen some work with numbers that do not match. I have about 50 key fobs and will sell them at $14 for 2 shipped. Any with the same number and a T will work with your system. There is a button sequence that enables the different lock functions. I do not have that sequence available. The number that matches the 92-93 systems ends in 103T. I believe the 104T is also compatible. The receiver for the 92-93 systems has green connectors. I do not know if the 94-96 receiver will work correctly with a 92-93 car. The 94-96 receivers have black connectors.

The programing is fairly simple. Have your receivers ready, and ground or cross the contacts of the programming connector. When the locks cycle (with each fob), disconnect the ground or shorting wire, and the system will be programmed. Some wagons have the programming connector on the driver's side, and some have them on the passenger's side. I believe the 92 and later are on the passenger's side and that you have to short the pins in the connector. You may still have to use the button pushing sequence to access or delete certain functions of the remote lock system.

Thanks Fred,
You're usually the first to jump in, always with a very detailed answer.
I certainly appreciate it, and I'm sure others do as well.