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Hi, I'm Diane and I'm happy to help you today.
Are you the tenant administrator? If not, you need to contact your IT admin for help - they can reset your authentication methods.
If you are the only tenant admin, you will need to call Microsoft support, and after proving you are the tenant owner, will help you get back in. https://learn.microsoft.com/en-us/microsoft-365/admin/get-help-support?view=o365-worldwide#phone-support
Let us know how it goes, we're here to help you further if needed.
-- Diane
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