I have this issue on both windows and mac computers.
I just had it happen to me, but just once on Nintendo Switch. Unfortunately, while trying to find my way anywhere, I died and lost all my recently upgraded stuff. Ug. The next time I went through the portal, it worked.
I tried loading on on iPad Air 2, iPad 4, and iPhone 11 Pro and also doesn’t work on any of them. It’s either freezing on the loading page or while signing into Microsoft account. Please fix asap.