Hi rosignol,
I’m Cathy, an Independent Advisor.
It's really sad that you're going through this situation.This problem occurs because there are duplicate tokens in the key chain.To resolve this issue, delete any cached passwords for the account and also remove any modern authentication tokens from the key chain,For specific steps, please visit the link below:
https://docs.microsoft.com/en-gb/outlook/troubl...
Hope this can help you.