OCOM changing device visibility failed

Hello,

Im working in an OCOM implementation for a Service Provider, they want that when a PDF report is created for a customer, no information about the Core is included to the final customer, so I created a realm in OCOM, and im trying to assign that realm to the device under plataform devices. But when applying the realm an error is showing stating that "Changing device visibility failed"

I really dont know if thats the best config to the request from the customer.

Does anyone know whats happening or what is causing that error? Or is there another way to implement this?