Microsoft Teams Sign-In Problems: How to Fix Login

Getting stuck in a Microsoft Teams sign-in loop — where Teams keeps redirecting you back to the login screen without ever letting you in — is one of the more frustrating issues you can encounter. Sign-in problems can also appear as error codes, blank authentication screens, or a prompt that accepts your password but then fails silently. Most of these problems come down to corrupted credentials, cached tokens, or a conflict with your organisation’s identity settings. Here is how to work through each cause systematically.

Sign Out and Sign Back In

The simplest first step: if Teams is open but stuck or looping, click your profile picture in the top right corner and choose Sign out. Close Teams fully via the system tray, then reopen it and sign in fresh. This clears any session state that may have become invalid.

Clear Saved Credentials

Windows stores Teams authentication tokens in the Credential Manager. Stale or conflicting tokens are a common cause of login loops.

Windows

1. Open Control Panel > User Accounts > Credential Manager.
2. Click Windows Credentials.
3. Look for any entries containing Microsoft, Teams, MicrosoftOffice, or msteams.
4. Remove each one.
5. Restart Teams and sign in again.

Mac

1. Open Keychain Access (search with Spotlight).
2. Search for Microsoft Teams and msteams.
3. Delete any matching entries.
4. Relaunch Teams and sign in.

Clear the Teams Cache

Corrupted cache data can cause authentication to fail even after entering the correct credentials. Clearing the cache is often the single most effective fix for sign-in loops. See the full guide on how to clear the Microsoft Teams cache for step-by-step instructions for both classic and new Teams.

Delete the Teams Identity Folder

Beyond the general cache, Teams stores account identity data in a separate folder. Deleting this can break a persistent login loop.

Classic Teams (Windows)

1. Quit Teams completely.
2. Open %appdata%MicrosoftTeams in File Explorer.
3. Delete the identityCache folder and the Cookies file.
4. Relaunch Teams.

New Teams (Windows)

1. Quit Teams.
2. Navigate to %localappdata%PackagesMSTeams_8wekyb3d8bbweLocalCacheMicrosoftMSTeams.
3. Delete the EBWebView and Auth folders if present.
4. Relaunch Teams.

Check Your Account Is Licensed

If you can sign in to Teams on the web (teams.microsoft.com) but not the desktop app, the issue may be a licensing or tenant configuration problem rather than a local one. Ask your IT administrator to confirm that your account has an active Microsoft 365 licence with Teams included and that your account has not been recently moved between tenants.

Try Signing In via the Web First

Open a browser in private/incognito mode and navigate to teams.microsoft.com. Sign in there. If the web version works, the problem is isolated to the desktop client. You can continue working via the browser while you resolve the desktop issue.

Disable or Remove VPN

Some VPN configurations interfere with the OAuth authentication flow that Teams uses to sign in. If you are connected to a VPN, disconnect it temporarily and try signing in. If that works, you may need to add Teams’ authentication endpoints to your VPN split-tunnel configuration.

Check Conditional Access Policies

On managed corporate devices, Azure Active Directory Conditional Access policies can block sign-in if your device is not compliant — for example, if it lacks the required certificates or Intune enrolment. Error codes such as AADSTS50076 or AADSTS53000 usually indicate a Conditional Access block. Your IT team will need to resolve these.

Reinstall Teams

If nothing above resolves the issue, uninstall Teams completely, delete the residual app data folders, and perform a clean reinstall from the Microsoft Teams download page. For new Teams on Windows, use the Microsoft Store or the Teams download page to get the latest version.

Related Issues

Once you are signed in successfully, if you notice calls disconnecting, see the guide on Microsoft Teams calls keep dropping. If your calendar is not syncing correctly after signing back in, Microsoft Teams not showing Outlook calendar meetings covers the usual causes.

For microphone issues that appear after a sign-in or reinstall, see Microsoft Teams microphone not working.

Common Sign-In Error Codes Explained

Teams sign-in errors often come with specific error codes that point to the cause. Here are the most common ones and what they mean:

• AADSTS50076 — Multi-factor authentication is required but was not completed. Open Teams in a browser first to complete the MFA challenge, then try the desktop app.
• AADSTS53000 — Conditional Access policy is blocking sign-in because the device is not compliant. Contact your IT team to enrol the device in Intune or resolve the compliance issue.
• AADSTS700016 — The application was not found in the directory. Usually indicates a tenant configuration problem — your IT team will need to investigate.
• AADSTS50020 — The user account from an identity provider does not exist in the target tenant. Common when switching between personal and work Microsoft accounts or after a domain migration.
• CAA20004 or CAA30194 — Authentication library errors on the desktop client. Clearing credentials from Credential Manager and the Teams cache resolves these in most cases.

Try the Teams Web App as a Temporary Workaround

If you need to keep working while resolving a desktop sign-in issue, the Teams web app at teams.microsoft.com has near-full feature parity with the desktop client. Most meeting, chat, and calling functionality is available in the browser. Use Microsoft Edge or Google Chrome for the best compatibility.

For a full index of every Teams guide and troubleshooting fix on Serverman, see the Microsoft Teams complete guide and troubleshooting hub.