hornet 554t remote won't transmit

I have a Hornet 554t. I am on my second 2-way remote and now it isn't working. It is a Valet 477t. The remote receives the 2-way transmissions but won't send any signals. If I use my 1-way tx to arm/disarm the 2-way will show the status just fine. When I push buttons on the 2-way tx the lcd shows that it is transmitting, but the truck doesn't respond. I've tried new batteries and reprogramming the tx. It won't reprogram because the tx isn't sending any signal. My original remote did the exact opposite. It would send signal but not receive any 2-way info. Any ideas?

Thanks Mark. I did take it apart to make sure the two boards weren't loose. I hadn't thought to check to make sure the solder joints for the plugs was solid. I'll check it out.