My son drives a 2001 V70. Right now you can not use the key to lock or unlock it which means it isn't secure to go places like his school. You cannot use the switch on the inside either but even if you could lock it, there would be no way to get back into the vehicle. A local repair facility thought it was the Master Power Window Switch part number 9452959. I have replaced that but while the windows go up and down, the locks are still unable to lock or unlock.

I've never seen a vehicle that when you put the key in the lock it will not manually lock or unlock the door. What else should I be looking at to solve it?

 

Sound like the actual lock tumbler got switched out, or just went bad. And if all the locks (if more than one) don't work with key, than someone replaced the actual ignition with an after market or used ignition/key.
My suggestion, but a new key, vin matched from the dealer. I bet that works in your locks.
Good luck.