what are you using for a signal source to the subwoofer? An AVR?
If you have gremlins in your home (I have 21 grand kids) its possible an AVR setting in bass mgt got changed. Running your setup for speakers is a quick way to define if the system thinks your sub is OK.
You should have an option to run sound to L R, and SW during setup. If it doesn't work there, then I'm with Pogre: check cables or the sub itself. If setup drives sound to the SW, but normal play doesn't, it could be an LFE + sub setting that's out of kilter.
Pogre has killer subs and if anybody knows how to get 'em to work, it would be him.