It turns out it was a fuse.
For the archives....
We had a dead shift panel on our Allison B500 transmission. The retarder applied light was also on. I checked the fuses in the battery compartment, and they were all good (that is where the main ATEC fuses and ECM fuses are located). I rebooted the ATEC, no go. I checked all sensors and connectors on the tranny, no joy. I checked the connector on the back of the shift pad, all good, but still no joy.
I knew there had to be something else, and it had to be simple. Sure enough, in the front junction box, far left corner, very bottom of the box, is a fuse. That is where power for the keypad goes through. That fuse was blown. I replaced it, and we were set.
It took me two hours to find a REALLY simple fix. At least we got it.
And thanks to Clifford for calling. I am sure that I found that fuse, because he called. I was on the phone with someone else, when his number appeared on my phone. Almost at the exact same time, I found the fuse. Figured it had to be because he left me a voice mail is why I found it