Hi Christopher,
The error message you provided indicates that the user does not have a mailbox assigned or a license associated with their account.
To resolve this issue, you can try the following steps:
- Verify License Assignment: Make sure that the user has been assigned a valid Microsoft 365 license, specifically the license that includes Outlook. You can check the license assignment in the Microsoft 365 admin center or through the Microsoft 365 admin portal.
- Assign Mailbox: Ensure that the user has a mailbox assigned to their account. In some cases, a mailbox might not have been automatically created for the user. You can assign a mailbox to the user using the Microsoft 365 admin center or PowerShell commands.
- Wait for Propagation: It can take some time for changes to propagate across Microsoft 365 services. After making any changes to license assignments or mailbox assignments, give it some time and try accessing Outlook again.
- Contact Support: If the issue persists, it's recommended to contact Microsoft support for further assistance. They can help investigate the specific error and provide guidance tailored to your situation.
Please let me know if this is helped you.