Im currently having this issue. Did you ever find a way to fix it? It just killed our minecraft 2 week phase :/
What this bug does is it makes it impossible to ever make a realm ever again it seems.
I paid for the realm then once I got the splashscreen that said i was ready to add a realm. I pressed back which caused my game to break and for me to be doomed, never to manage my minecraft realms
This is happening to me on a Playstation 5.