I have three children with three seperate switch consoles.  Lately I am being required to log them in to the microsoft account mutliple times a day.  Last night 8/13 I spent 30 minutes signing one of my children into his account trying force close of the app.  Restart of the switch eventually I was able to get them signed in.  Tonight all three of my children were signed out.  I got all of them signed in we played for 40 minutes.  Two of them went to bed and the my oldest and i left that game and went to play on another save in his account.  It showed him as signed in on the entry page of they game but when he would enter the save I couldn't see the game and when he went to the invite screen it said oops something is wrong with your microsoft account.  Because this is occuring on three different switches it can not be a switch issue.  I am playing from a PC and have not had a problem.