Held Controller

Is our guitar for Guitar Hero defective?
My daughter just got Guitar Hero 2 for PS2 for Christmas. We installed new batteries in the guitar, but the LED indicator is still flashing. According to the directions, that means it’s not picking up a signal from the controller. What could be the problem? The game itself plays and we can use the hand held controller to select songs and so forth. But the guitar will not play at all.
Unplug the receiver from the PS2 and retry the process. I don’t know. Guitar Hero 2 is my favorite, nice choice. Good luck!