Passenger door won't unlock. please help me
 

It won't open from inside or outside. When I push the button from the outside there is no longer a beep. When I push the unlock button from inside on the driver side, the lock, unlock button on the inside of the passenger side moves back and forth but the door is still locked.

Also I have had about 2 or 3 passengers in the last five years so I would say I have used the passenger side door maybe 50 times compared to thousands of times on the driver's side.

Is there a fuse for the door unlock?

What mechanism controls door unlock?

Thanks in advance