Immediate Fix
The most common reason Word prevents you from signing in is a corrupted credential cache. To fix this immediately, you need to clear the Windows Credential Manager.
Close all Microsoft Office applications. Open the Control Panel, navigate to User Accounts, and select Credential Manager. Click on Windows Credentials.
Locate any entries starting with “MicrosoftOffice16” or “mso” and remove them. Restart Word and try signing in again. This forces the application to create a clean authentication token.
Common Sign-in Error Codes
| Error Code | Probable Cause | Quick Solution |
|---|---|---|
| 0x80048820 | System Clock Mismatch | Sync Time & Date |
| 0xCAA70007 | Network Timeout | Disable VPN/Proxy |
| 0x80070005 | Permission Denied | Run as Administrator |
Technical Explanation
Microsoft Word uses Modern Authentication (ADAL) to verify your subscription. This process relies on OAuth tokens stored locally on your machine. When these tokens mismatch with the server-side state, a login loop occurs.
Another technical factor is “Workplace Join.” If your device is registered with an organization, the Microsoft 365 identity provider may block personal account sign-ins to prevent data leakage.
Network security protocols like TLS 1.2 are also mandatory. If your operating system is outdated, Word cannot establish a secure handshake with the login servers, resulting in a silent failure.
Alternative Methods
If the Credential Manager fix does not work, you can force your device to unbind from the current identity state using the Command Prompt. This is particularly useful for enterprise users.
dsregcmd /leave
# This command unregisters your device from Azure AD
# Restart Word after running this to trigger a fresh login promptRegistry Reset
You can also clear the Identity registry key. Navigate to HKEY_CURRENT_USER\Software\Microsoft\Office\16.0\Common\Identity. Delete the Identities folder. Word will regenerate this folder upon the next launch.
Finally, ensure that “Office Feature Updates” are not pending. An outdated client version may lack the necessary security patches to communicate with the latest Microsoft 365 login endpoints.