I am going to make 2 assumptions:
1. The battery has died or you've figured out a solution
2. You know you have to move the dial on the on/off button clockwise; if it is pointed down, it is locked.
If you didn't know #2, (and always had it in the "unlocked" mode) now you do.
In any case, I believe this item has a 1 year warranty. Call Panasonic and ask for help. You might also call BestBuy -- but, I doubt they'd respond.