It's mains motor built into the spindle.
Ok so it's a domestic roller shutter garage door. It will be something like this...
There is a wiring guide on page 6, and it is similar to mine. The motor has three terminals, common neutral, one up, one for down. If when you press the door up button, you check for voltage between neutral and the up terminal, there should be mains voltage. If there is, then the motor has an issue, if not the issue is on the PCB,
The motor includes two internal limit switches, one for up, and one for down. They use an arm, on a long thread, rotated by the motor, and hitting a micro-switch - all of which is tucked away in the motor housing/spindle. There is a chance that the open limit switch is faulty/open circuit.
The entire replacement motor can be had, if necessary, for around £60, via ebay - but there are several motor models, get the correct model details from his motor's label. The motor includes a deliberate weakness in the shaft, which will snap, if the motor comes under too high a load.