Have you calibrated the FBV?  Downloaded the latest firmware?

The Wah is accessed by stepping on the toe of the pedal very hard - you need to do it standing up with shoes on when it's new!

To calibrate:

1)  Hold D while powering on the FBV. Upon release, the pedal display will read “1”.

2)  Press and hold the pedal toeswitch until the 7 segment display changes to “2”.  This should occur instantly.

3)  Set the heel to the heel (minimum) position, press the D button.  The 7 segment display will change to “3”.

4)  Set the toe position (maximum) and press the D button.  The tuner LEDs above the 7 segment display will light.

5)  Move the pedal and verify that the tuner LEDs sequentially turn off as the pedal moves to the minimum position, and refills when moved to the maximum position.
6)  Press D to exit 

Here's a document on how to update the firmware:  http://line6.com/support/docs/DOC-1652