I'm having this issue too. I've had this tank for a couple/few months now. Never had a problem with the AFC. I was able to get it to move just enough to have a little airflow. I've tried rubber bands, rubber gloves, needle nose pliers -- which pushing the tip of one "nose" and pushing to the side is what opened it up a tad. I can vape with it like this if I enjoy a whistling sound as well -- which I don't.
The only thing I can think of why this even happened is when I had to open the tank to change the coil I overdid something, but I'd think the AFC would be stuck completely closed.
This isn't my most fave tank so I wouldn't be as upset if I hadn't just ordered a box of coils. It does spit out some juice from the air holes when vaping. That's with the AFC all the way open.