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

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