I have had this issue myself on numerous occasions. I have an AM-1 running an accessory project, and an LM-3 loaded with the accessory program and a project.
Both of these will do exactly as you describe when I "find" them on a Hand Controller.
I can make it work, but I'm not sure exactly what the fix is. I think the only critical step is loading the accessory project you are using on to the hand controller, but I haven't tried just that yet. This is the procedure I follow that fixes it....
1. Remove the Accessory Module from the HC
2. Clear the Active Loco list
3. Connect the HC to PC with USB cable and Use Rail Pro Assistant to do the following...
4. Load the correct Product Program for the AM you are using
5. Load the Accessory Project you are using
6. Find Product to get the Accessory back into the HC
After doing the above procedure, my AM will show up on the HC and opening it displays the correct buttons that I have programmed.
Another note about using LM's loaded with the Accessory Project Program:
Your LM Accessory will show up under both Locomotives and Accessories. If you access it from the Locomotive screen, RP gets confused and thinks it's still a loco and does not display the programmed buttons. Switching to the Accessory screen now gives the same 'blank screen' result. To fix, Clear the Active Loco list.
When on a locomotive control screen, switching to the Accessory by tapping the photo and picking it from the loco list does not result in the 'blank screen' problem
I've not reported this as a bug to Ring, but it probably should be.
