Hi @Sales ,
Based on your description, this error message may occur when your subscription is no longer active or has been blocked by the admin. I suggest you may firstly refer to following information to narrow down:
- Login Office 365 admin center >Billing >Your products, make sure the license is still in active:
- Try to re-assign the license, wait for a while to let changes take effect.
- Use browser InPrivate mode (to avoid caches), and confirm if user can access Outlook Web App.
If issue still exists, please provide more detailed information, so that we can give more appropriate suggestions.
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