IN 30 SECONDSFull read: 4 min
- If the browser works but the app doesn't, it's the desktop app. If both fail, it's the account or network.
- A missing or outdated WebView2 Runtime is the most likely cause of a blank sign-in window.
- Error codes on the sign-in screen point to the exact cause, from network to Conditional Access.
The sign-in window opens white or nothing loads at all. Before you spend an hour guessing, run the two-second browser test below. It tells you exactly which half of the problem you are dealing with.
Do this first: the browser test#
Open teams.microsoft.com in your browser and try signing in.
| Result | WHAT IT MEANS |
|---|---|
| Browser works, app does not | Desktop app issue. Focus on WebView2 and the manual fix steps below. |
| Browser also fails | Account or network issue. Start with the diagnostic tools below, then jump to steps 4 and 5. |
Browser works, app does not
- What it means
- Desktop app issue. Focus on WebView2 and the manual fix steps below.
Browser also fails
- What it means
- Account or network issue. Start with the diagnostic tools below, then jump to steps 4 and 5.
Run Microsoft's built-in diagnostics first (admin required)#
If you have a Microsoft 365 admin account, these two tools check the affected account automatically and identify the root cause in seconds. Run them before attempting any manual steps.
Teams sign-in diagnostic#
Runs in the Microsoft 365 admin center. Enter the affected user's email address and it checks their account configuration for known sign-in blockers. Requires Microsoft 365 admin account. Not available in Government or 21Vianet tenants.
Remote Connectivity Analyzer#
Tests whether the user's account can actually reach Microsoft's authentication endpoints. Catches network and connectivity blocks that the admin center test does not cover. Not available in GCC or GCC High Government environments.
Install the WebView2 Runtime#
Download WebView2 Runtime, choose the Evergreen Standalone Installer → install → restart your PC → try Teams again.
Manual fixes in order#
If WebView2 did not fix it, or the diagnostics did not find an issue, work through these steps in sequence.
1. Update the Teams desktop app#
Teams updates automatically, but occasionally falls behind. Check for a pending update before anything else.
Teams → top-right menu (three dots) → Check for updates
2. Check your system clock#
A wrong time or time zone silently breaks the authentication tokens Teams relies on. Make sure both are set automatically.
Settings → Time & language → Date & time → turn on "Set time automatically" and "Set time zone automatically"
3. Clear cached credentials#
Windows stores login tokens for Teams and Office. When those go stale, they block a fresh sign-in. Delete them so Windows fetches new ones.
Credential Manager → Windows Credentials → remove any entries containing "Teams" or "MicrosoftOffice"
4. Reset or fully reinstall the Teams app#
A corrupted installation can cause a blank sign-in window even with WebView2 in place. Try the Reset option first. If that does not work, uninstall fully, delete the leftover Teams folder, then reinstall clean.
Settings → Apps → Microsoft Teams → Advanced options → Reset
For a full reinstall: uninstall Teams, then delete the %appdata%\Microsoft\Teams folder, then reinstall from teams.microsoft.com/downloads. Right-click the installer and choose Run as administrator.
5. Pause your VPN and antivirus, then test on a mobile hotspot#
Security software and VPN tunnels can intercept the sign-in flow without showing a clear error. Temporarily disable them, switch your PC to your phone's mobile data, and try again. If it works there, the issue is your local network or a security tool blocking Microsoft's authentication endpoints.
Check your error code#
Teams displays an error code on the sign-in screen when something specific is wrong. If you can see a code, find it below. It tells you exactly what to do next.
0xCAA82EE7 / 0xCAA82EE2: No internet or network connectivity issue#
Teams cannot reach Microsoft's servers. Confirm the device has internet access. Then use Microsoft's Network Assessment Tool to verify the required IP addresses and ports are reachable. If you are on a corporate network, your firewall may be blocking the endpoints Teams needs. Check the Microsoft 365 URLs and IP address ranges list.
0xCAA20004: Conditional Access is blocking the sign-in#
A Conditional Access policy in your tenant is preventing this device or user from signing in. This is an admin-level fix. The policy may require a compliant device, an approved app, or MFA that the device cannot satisfy. Check your Conditional Access policies for Teams in Entra ID.
0xCAA70004 / 0xCAA70007: Office 2016 connection issue (also affects other Office apps)#
If this error appears in Teams and you are also having sign-in issues in other Office apps, it is likely an Office 2016 build conflict. See Microsoft's guidance on connection issues after updating to Office 2016 build 16.0.7967.
References: Why am I having trouble signing in to Microsoft Teams?, Teams stuck in a login loop, Resolve sign-in errors in Teams.
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