sub does not move

I had 2 viper subs in my blazer before i got it bagged. while my blazer was getting bagged the subs were taken out for like two months. This weekend one of my friends went to put the sub in but it would not work. The voice coils is fine but when you push on the middle of the sub it does not move at all. I was just wondering what is wrong with the sub and also what might have caused this? Also I was wondering if anyone knew had to fix it if you can?