The doors in the back will not open from the inside or outside of the car. First it was the one and then shortly after that the other one. Could it be a fuse?

Pretty unusual that both rear door are not opening....from either the inside or outside. You have probably tired these but here goes.... (1) using the drivers door power lock button unlock the doors...can you hear anything happening at the rear doors? (2) your car may be too new, but may have manual lock buttons or sliders. (3) there is a chance if you hear nothing at the rear doors when you try #1...you may have a bad connection ...all the doors are on the same fuse, but the wiring goes under the carpet. You will need to find a service manual for your car and find the wire. The real problem is the door panels are almost inpossible to get off with the door closed.

I have a 1991 Buick lesabre the rear passenger door wont open from inside or outside I took door panel off there there away open it without using the door handle ?

The problem is actually tn the linkage from the outside door handle to the latch. What happens is the linkage builds up with corrosion. Even though everything looks ok, it prevents the arm on the latch in which this linkage connects to, from returning to it's home position. The system locks the doors when you drive and unlocks them when you put it in park. Because this arm didn't quite return to the home position, the door does not unlock. Some times you can get it to work by jiggling the outside lever up and down or lightly pounding on the outside of the door, followed by pressing the door unlock actuator button. The problem will continue to get worse however. The door panel needs to be removed and the arm on the latch connected to the linkage to the outside handle needs to get tapped or manipulated by moving that linkage, to it's home position. At that point the door can be manually or electrically unlocked and the door will open, The outside door handle is held on by 2 #6 metric bolts (10mm wrench or socket).. You have to undo the clip which fastens it to the door latch arm to remove it. If you clean up the handle pivot points and the linkage pivot points on both ends and lightly lube it with something like wd40 and reassemble, it will work properly until it builds up with corrosion again. And it will, especially as the doors rust out.