Need a POST request and GET request to help sign in M365 on my mobile phone

Brenda Chang 0 Reputation points
2026-11-09T01:44:05.64+00:00

I signed in M365 on my mobile & tried to download the app but it said having trouble signing in and got this message AADSTS900561: the endpoint only accepts POST requests. Received a GET request.

What to do?

Microsoft 365 and Office | Install, redeem, activate | For business | Other
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  1. Austin-H 8,810 Reputation points Microsoft External Staff Moderator
    2026-11-09T02:15:05.8833333+00:00

    Hello Brenda Chang

    This error generally occurs when the Microsoft authentication service receives an unexpected request during the sign-in process. It can sometimes happen if the authentication session is interrupted, such as when navigating backward in the browser.

    To help narrow down the issue, please try the following:

    1. Close your current browser session, reopen your browser, and sign in again through Microsoft 365.
    2. Try signing in using an InPrivate/Incognito window to check whether the issue persists on your mobile's browser.
    3. If the issue continues, clear your browser's cache and cookies, or try another browser.
    4. Alternatively, try to force close/clear Microsoft 365 app's cache then run it again.

    Those suggestions above and AI's responses are similar. Please try again and let me know if this issue re-occurs.

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

    Note: Please follow the steps in our documentation to enable e-mail notifications if you want to receive the related email notification for this thread.

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  2. AI answer

    2026-11-09T01:45:20.5266667+00:00

    You do not need to create a POST or GET request yourself; restart the download or sign-in from the Microsoft 365 app or official app store rather than reopening the failed sign-in page.

    If the error appeared in your phone browser while downloading

    1. Close the error page and all Microsoft sign-in tabs.
    2. Open a Private/Incognito tab and start the download or sign-in again. Do not use an old bookmark, copied login address, or the browser Back button. A stale or interrupted authentication session can send the wrong request to the sign-in endpoint.^1^
    3. If private browsing works, clear the normal browser’s cookies and cached data for Microsoft sites.
    4. If third-party cookies are blocked, temporarily allow them:
      • Chrome: Settings → Privacy and security → Third-party cookies → Allow third-party cookies
      • Edge: Settings → Privacy, search, and services → Cookies → turn off Block third-party cookies
      Also temporarily disable any content blocker, ad blocker, or privacy extension during sign-in.^2^
    5. Return to the official app store, search for Microsoft 365 Copilot, and install it directly instead of continuing through the failed browser redirect.

    If the app is already installed and the error occurs inside it

    1. Force-close Microsoft 365 and reopen it.
    2. Remove the account from the app, then add it again using Sign in inside the app.
    3. Confirm that you use the account associated with your Microsoft 365 subscription—either the correct personal Microsoft account or your organization’s work/school account.^3^
    4. Update the app from Google Play or the Apple App Store.
    5. If it still fails:
      • Android: Settings → Apps → Microsoft 365 → Storage → Clear cache. If necessary, use Clear storage/data, but this signs you out and removes local app settings.
      • iPhone: Delete and reinstall Microsoft 365, then begin a fresh in-app sign-in.

    If this is a company Microsoft 365 account

    If browser sign-in works but the installed mobile app still fails, contact your organization’s IT administrator. Mobile access can be affected by Conditional Access, approved-app, or app-protection requirements that differ from browser access; only the tenant administrator can inspect those policies.^4^

    Provide the administrator with the AADSTS900561 code, timestamp, request ID, and correlation ID shown on the error page, but do not post those identifiers publicly. Microsoft documents these fields as diagnostic information for authentication failures.^5^

    References

    1. EMAIL ACCOUNT/HOTMAIL - Microsoft Q&A
    2. AADSTS900561: The endpoint only accepts POST requests. Received a GET request - Microsoft Q&A
    3. What you can do in the Microsoft 365 apps on mobile devices with a Microsoft 365 subscription | Microsoft Support
    4. Inquiry Regarding Microsoft 365 Mobile App Login Issue on Android 13 - Microsoft Q&A
    5. Microsoft Entra authentication and authorization error codes
    AI-generated content may be incorrect. Read our transparency notes for more information.

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