If it fails mechanically like the gear stripping internally it will have a grinding or whirring noise.
Sliding door on 2014 chevy van not opening.
Dodge chrysler caravan town and country sliding door will not open or close get this checked and done first.
If it fails electrically you will not hear the actuator try to operate when you try to lock unlock the door.
1999 gm chevy astro van sliding door got stuck open.
It would not move either way.
If it is engaged the door will not open from the inside by design.
The front lower bracket was wedged under the guide channel.
Check the child safety lock if the problem door is a rear door.
The rear door lock actuator can fail in two ways electrically or mechanically.