We had this Error message over all Apps:
Unable to fetch app definition. Error:User '622224' does not have a valied 'microsoft' account.
We could not use any App.
Then I logged in to appsheet.com with my Microsoft account.
Then choose my Account.
But it sent me back to the first picture. I choose again my account and it sent me back to the first picture and so on. I had to do this 5 times. Then I was logged in.
After that, all Apps where working again.
As you can understand this is very frustrating as we are using our Apps in Business.