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Just to clarify, are you trying to access the Outlook desktop app?
If yes, please re‑check whether your current plan is Exchange Online (Plan 1) or Microsoft 365 Business Standard.
As my research, Exchange Online Plan 1 only supports Outlook on the web and does not include the Outlook desktop application.
To use the Outlook desktop app with your work account, I recommend upgrading to a Microsoft 365 business plan that includes desktop applications, such as Microsoft 365 Business Standard.
You can refer via: Compare Microsoft Exchange Online Plans Microsoft 365
If it’s not the scenario mentioned above and you’re actually experiencing an issue with a Microsoft 365 Business Standard license, and Outlook Web also isn’t working, could you let me know whether any error message appears, such as: “Mailbox not found”, “Your admin has not assigned you a license” or “Something went wrong – X-ClientError”
Please feel free to correct me if I misunderstood your request. If you have any additional concerns, feel free to comment below. I would be more than happy to assist.
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