A work around for this problem I have discovered is as following:
1) connect iPad to iTunes.
2) iPad Summary -> File Sharing -> Apps -> Minecraft
3) Rename the file XBLStoage.json to XBLStoage.json.old
4) Start minecraft it will recreate the file and minecraft will start without crashing.
I have the same issue with both my kids accounts. I changed some settings on xbox live so they could add each other and now on startup of minecraft pocket edition both iPads crash.
How did you resolve this? I don't want to reinstall as my son will lose a lot of worlds he created.
There are no ways to backup worlds, you really should add this.
Same issue here. Game doesn't start up on iPad (5e generation - iOS 13.3) and iPad Pro (2018 - iOS 13.3).
It works however on iPad Mini with iOS 12.
As a lot of people seems to have issues with the same problem. It should be something related to a patch that has been rolled out or some services now working correctly.