login issues

Ondien Lindeman 20 Reputation points
2026-09-17T21:08:00.46+00:00

“I created a new Microsoft 365 Business tenant today. The tenant exists and I received the confirmation email with admin username [Moderator note: Personally Identifiable Information removed]@GuardienovaSystems.onmicrosoft.com, but Microsoft sign-in says the username does not exist. I am the sole Global Administrator and cannot access the Admin Center. Please check whether the initial admin account failed to provision and restore/create the admin identity for the tenant.”

Microsoft 365 and Office | Subscription, account, billing | For business | Windows
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Answer accepted by question author
Ivory 1,745 Reputation points Independent Advisor
2026-09-17T21:43:08.6066667+00:00

Hi Ondien,

May I ask if you have updated your custom domain and are now using it for your email?

For example: ******@yourcompany.com

In many cases, if you have changed your UPN (User Principal Name) to include your custom domain, you must use that custom UPN to sign in rather than your original onmicrosoft.com account.

I hope this provides enough clarity and helps you stay inform with your current situation.

If you have any questions or need further assistance, please feel free to share them in the comments on this post so I can continue to support you.  

If the answer is helpful, please click 'Yes' and kindly upvote it.

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