If possible I'd take it to a certified Hasselblad repair person.

I believe you can go in through the back and unscrew a small plate where the cocking mechanism is at the bottom of the lens opening.

I've had this happen too but didn't want to mess around with this so I took it to a repair person and they fixed it in a few minutes.

Once the lens is removed from the camera, remember to take a coin and recock the shutter.

Michael MCBlane