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How to Fix Microsoft 365 Error AADSTS900561 in Word and Office Apps
Question details
Users are encountering Error AADSTS900561 during authentication in Microsoft 365 apps, causing applications like Word to become unresponsive or greyed out.
- Product
- Microsoft 365
- Device & OS
- Windows
- Scenario
- Authenticating or logging into Microsoft 365 desktop applications.
- Observed behavior
- The system throws Error AADSTS900561, stating an endpoint received a GET request instead of a POST request, resulting in greyed-out apps or Word stopping to respond.
Ensure your computer is connected to a stable internet connection and save any open documents before initiating the Office repair process.
Perform an Online Repair of Microsoft 365
Running an online repair can fix corrupted installation files and resolve the AADSTS900561 authentication error.
The Online Repair tool goes beyond a quick repair by completely refreshing your Microsoft 365 installation files from the cloud. This is often necessary when core authentication components become corrupted.
Right-click the Windows Start menu and select 'Apps and Features' or 'Installed apps' depending on your specific Windows version.
Scroll through the list of installed applications and find your Microsoft 365 or Office installation entry.
Click the three dots next to the app (or select it directly) and choose 'Modify'. If prompted by User Account Control, click 'Yes' to allow changes.
Select the 'Online Repair' option and click 'Repair'. Follow the on-screen instructions to complete the download and repair process.
Once the repair finishes, restart your computer and launch Microsoft Word to try signing into your account again.
Clear Stale Office Credentials in Windows
Clearing old or corrupted cached credentials can force Microsoft 365 to establish a fresh, successful authentication connection.
Try WPS Office for a Hassle-Free Experience
If Microsoft 365 authentication errors continue to disrupt your workflow, consider switching to WPS Office. It is a lightweight, free alternative that offers excellent compatibility without complex login requirements for local editing.
- 1. Download the Installer: Visit the official WPS Office website and click the free download button.
- 2. Install WPS Office: Run the downloaded setup file and follow the quick installation prompts.
- 3. Open Your Documents: Launch WPS Office and open your existing Word, Excel, or PowerPoint files instantly.
Frequently Asked Questions
What does Error AADSTS900561 mean in Microsoft 365?
Error AADSTS900561 is a technical authentication error indicating that an endpoint received a GET request when it required a POST request. In simpler terms, a communication mismatch occurred during the sign-in process, causing your Office apps to fail to authenticate your account.
Will an Online Repair delete my Word documents?
No, performing an Online Repair of your Microsoft 365 installation will only refresh and fix the application files and core settings. Your personal files, documents, and system data will remain safe and completely unaffected.
Why are my Microsoft 365 apps greyed out?
When Office apps cannot verify your active subscription due to an authentication error like AADSTS900561, they may enter a reduced functionality mode. This mode greys out most tools in the ribbon and prevents you from editing or creating new documents until you successfully sign back in.
