I've attached a screenshot of the screen I'm returned to after the purple loading screen. This is from my iPhone, but the message was the same on Windows. I'm using the Swedish translation, but I trust you can look it up in translation files. You can also see my username in the screenshot, and if you need authorization to access my account and realm for debugging purposes, you have my permission.
My MCPE-114062 was duped into this, but I can't see a workaround. I've tried logging out and in again using my account but that didn't seem to work.
Since Realms has always taken a minute or two to start for me, this became the last straw, and I've canceled my Realms subscription in favor of more expensive self-hosting that I can at least make work.