EMAIL ACCOUNT/HOTMAIL

Hi Maria Ntelaki,

Welcome to Microsoft Q&A forum. 

Please note that our forum is a public platform, and we will modify your question to hide your personal information in the description. Kindly ensure that you hide any personal or organizational information the next time you post an error or other details to protect personal data.

The AADSTS900561 incident (endpoint only accepts POST but received GET) is typically caused by a broken sign-in session (stale cookies/tokens) or by browser settings/extensions interfering with the authentication process.

Please try the steps below:

• Sign out completely, close all browser tabs/windows, then sign in again via Outlook on the web (avoid using old bookmarks or links).
• Try signing in using an InPrivate/Incognito window, or on a different browser/device.
• Temporarily allow cookies (including third‑party cookies) and disable any ad‑blocking or privacy extensions, then try again.
• If the incident persists, clear your browser cache/cookies (especially for Microsoft/Outlook sites) and try signing in again.

Please feel free to let me know if you have any further updates, thanks.

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