Does the button look blue? If so, you have one of the older boards, and the placement of the LED light was kind of crap and you could've broken it. It could be on, but just no indicator.
Another possibility, if it's that type of board only, there's gunk in the button itself. It's risky to open and clean b/c you might not be able to put it back together if you don't know what you're doing
Represent the old, long 68/45k tanks!
Rockin' a Champagne Eigen'd NXT Shocker