Well according to Spektrum, that combo is compatible. And I belive is what they use for their dx2e factory rx/TX combo. It is possible that one or the other has gone bad or is factory defective.

If you're following the binding instructions as per the manual and still have trouble, I'd either try a different receiver to see if the radio will bind. If that doesn't work I'd call Spektrum and ask them about getting a replacement transmitter.