User is unable to log into their Outlook 365 account in both their Outlook client and via https://outlook.office365.com OWA. Outlook will just continually prompt for credentials. OWA will give one of several error messages indicating either, a license is not associated with the account, the mailbox is disabled, the mailbox isn't available or bad request. Bad user name or password.
Cause:
The users Office 365 account is missing an association to the Office365 ProPlus and/or Exchange Online (Plan1) license in the O365 Admin Console.
Solution:
Escalate ticket to Systems to have license added to the account.