Dont know if this is any help but had the same problem with my sunroof, when i turned the dial, nothing happened, but when i pressed the button and held it in as well the sunroof would move in stages then stop, so knew there was power to the motor.
Took the motor of the car and bench tested it, turned ok but stops and starts.
Turned out i had a fault on the circuit board at the motor, i ended up replacing the motor complete with the circuit board.
Give it a try to see if it is the same problem, you will need a hex key to manually wind the motor back as it may stop halfway open.
Dont know which fuse is for the sunroof.
Try e-bay (one for sale at the moment) for a replacement motor, very very expensive at the dealers, sit down before you ask for a price.
If you have any luck remember to grease the slides on your sunroof. Best of luck.