Well by now you may be ready to rip it out, but before you do, double check the dip switches especially #12 it should be OFF.
Then do what Brian suggests and redo the diagnostic mode, if you are then still perplexed call Rostra as they are helpful.
The one time I didn't get an answer they called me back in 15 minutes just from my caller id since I didn't leave a message.
Do the green LEDs under the switches come on when you turn on the ignition? Does the center green LED light up when you do get it to work?
I just returned from Chicago and the Rostra worked great whenever I used it, even when I adjusted it up and down again and again for the monotonous, all too frequent construction zones.
Good Luck.