Is there a procedure in your documentation that explains the steps to match the camera? I seem to recall that there were in the directions I received. But mine are in the MH which is in storage at the moment. I'll be going to check on it one day this week, so if you don't have a solution i will get the installation manual I have.
Garmin obviously knows the ID number for the devices, so it should be able to preload them without actually hooking them up.
One quick thought. Do you have the BlueTooth enabled? I'm not sure if the camera needs it but mine is on because I link to my phone.
1999 Newmar MACA 3796 F53 6.8L
2016 Ford Edge Sport
Roadmaster Sterling A/T with Brake Buddy Select