I had problems with my sunroof on my recent purchase. The rear of the sunroof was lower than the front, I conceeded and bought a Haynes manual which explained how to take it apart and put it back together again.
My problem was a two fold, a rusted support arm on the front wind deflector which wasn't a problem opening, just shutting - which I replaced. The second problem I discovered after part opening the roof, was that a nut and bolt had come undone on the height adjustment part and thrown it out of sink. My roof did open, it just went back slowly at an angle. When it came to the replacement support arm I went to a breakers yard, and couldn't open the roof of the donor car, so the guy with just his fist clenched started to open the roof with the handle, and thumped the rear part of the panel a few times to loosen it and it popped open. A bit of brute force worked in that scenario.
The cause may be that it is just stuck around the seal and needs assistance, or it could be more serious.
Hopefully it is just stuck.