There was a return-filter on the line at the junction box. It's not there now.
The router is new enough it wasn't in their inventory of MAC addresses for compatible devices. That's fixed.
Check, check, check, sync, everything happy.
No service charge for the call.
The border website wouldn't download the registration app to my machine, but I still had the CD that came with the self-install kit. Installed and ran.
Once the connection was up, plugged in the wireless router, reset both devices, and everything is running fine. Including the equipment in the studio on the other side of the wireless bridge. Bridge is now bridging to another room, not just to the same shelf.
900mb-1.2gb speed test, and that's from the other side of the wireless bridge.