Does it lock properly with the fob? If it doesn’t, then it is possible that there is a fault in the wiring to the motor, look at the wires that get bent as they go into the door.

If the motor is receiving a signal, but it is not high enough voltage, check the connections between the lock motor and the central lock controller.

If you want to check the lock motor, it is just two pins, one positive and one negative for locking, and other way around for unlock.
Try with it connected to the lock mechansim and disconnected. If it works only when disconnected, try lubricating the lock.