I cannot believe this is still happening, have they even explained what caused it? I have 3 Outlook accounts & use Outlook 2013, sometimes the credentials pop up only comes up for 1, sometimes 2 but mostly all 3 & it is every time I open Outlook. Sometimes it takes 10 attempts to enter the password, other times it goes on much longer & there is no break between - as soon as I click save it pops up again.
What is most frustrating though is the response from Microsoft. I am using app passwords (& changed them when advised), I have the correct version of Outlook & I have it set to update automatically - all of this has been the case since this problem started yet nothing has improved.