New User Cannot Sign in

Dear Gigi,

As a forum moderator, I am not able to check your tenant or the new user's account directly. My role here is limited to providing general guidance you can apply from your side. That error usually means the user is entering an address that does not exactly match the username created in Microsoft 365, or the account has not finished provisioning. 

The email address and sign-in username can differ. Ask the user to sign in with the exact Username shown in Active users, for example: username @company.onmicrosoft.com

If the exact username is still not recognized, verify that the user appears under Active users, not Deleted users or Guest users. For a hybrid environment, confirm that the account synchronized successfully from Active Directory, since synchronized users must be managed through the organization’s directory-sync process.

For reference: Manage Microsoft 365 user accounts - Microsoft 365 Enterprise | Microsoft Learn

If the issue continues, could you let me know whether the user is signing in with the onmicrosoft.com address or your custom domain, and which page they're using to sign in? Please don't post the full address here, as this is a public forum.

I hope this helps. Looking forward to your reply.

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