Overdrive on rock band wireless guitar

I have had this problem once or twice myself. For me, I used to be familiar with the Guitar Hero controllers, which were very sensitive. As for Harmonix's rock band guitars, they are not as sensitive as guitar hero's and require a very deliberate motion when deploying overdrive. Next time you're playing, give it a deliberate tilt upward with a decent amount force. Also, if you bought it used, that could be a problem as well. Hope that helps.