Microsoft said that they are monitoring the servers and disabling authentication occasionally with the "old" auth method to hinder attackers. That's why you see your Outlook emails in Hub sometimes working, sometimes not.
A permanent solution would be for BB to switch to 2auth (or whatever the "new" auth method is called). There is no ETA. So in the meantime, setting your Outlook email in Hub via IMAP (as described in my previous post) is the only solution if you want to continue using BB Hub. 2FA won't do anything.