eM Client keeps prompting for password - MacOS Office365


As title says - the client keeps on prompting the password. It happens when client is opened or being synchronized.
When you type the password , the prompt instantly pops up again until Cancel is pressed.

The password is correct, because after the prompt cancel the client synces the emails just fine, emails are flowing normally.

Only one account is added to the client which is Office365 one. There are other folder, which emails are from old email. When syncing the Office365 account the prompt comes right up so it is the account that causes the issue.

Tried deleting and readding the account.

What could cause the issue, what else would you suggest to me to do?


Was this ever resolved? sounds like an issue with Office365 modern authentication.