2000 Volvo Wagon Locking Mechanism

Interior problem
2000 Volvo Wagon All Wheel Drive 140000 miles

I have a 2000 Volvo V70XC with a power locking problem. At roughly the same time the powerlock quit working on the tailgate and the "lock" button on the Key Fob quit working. The power locks will work when using the switch on the door panel - just not the tailgate. I don't think the Key Fob is bad, but I'm not sure. Could it be the receiver for the Key Fob? If so, where is it? What else could it be? This is a really annoying problem. It is hard to unlock the tailgate because it does not have a key. Have to reach from the back seat to do it.

Thank you.