Can't Sign In to Microsoft Teams — What It Means & How to Fix It

What Does This Error Mean?

Teams is refusing to accept your login or keeps looping back to the sign-in page. This is usually caused by a cached login token that has expired or gone bad. Clearing the Teams cache almost always fixes this.

Affected Models

Microsoft Teams for Windows
Microsoft Teams for Mac
Microsoft Teams on Web
Microsoft Teams Mobile

Common Causes

A corrupted or expired sign-in token stored in the Teams cache
Incorrect password or account that has been locked by your organisation
Two-factor authentication (2FA) failing or not completing
A Teams account conflict when multiple Microsoft accounts are on the device
A company IT policy or conditional access rule blocking sign-in

How to Fix It

Try signing in on the Teams web app first. Open a browser and go to teams.microsoft.com. If that works, the problem is with the desktop app only.

This tells you whether it is an account problem or an app problem.
Clear the Teams cache. Close Teams completely. Then open File Explorer and go to: %AppData%\Microsoft\Teams. Delete the contents of that folder (not the folder itself). Reopen Teams.

On Mac, the cache is at ~/Library/Application Support/Microsoft/Teams.
Sign out and sign back in. In Teams, click your profile picture, then 'Sign out'. Close Teams, reopen it, and sign in fresh with your email and password.

If you are stuck in a loop and can't reach the sign-out button, use the cache clear method above.
Check that your password is correct. Try signing in to office.com with the same account. If that fails too, your password may have expired or been reset.

Work and school accounts often have password expiry policies.
Remove the Teams account from Windows Credential Manager. Open Credential Manager from the Start menu, click 'Windows Credentials', find any Microsoft or Teams entries, and remove them. Then reopen Teams.

Old saved credentials can block new sign-ins. Removing them lets Teams start fresh.

When to Call a Professional

If you are on a work or school account and cannot sign in after trying these steps, contact your IT helpdesk. They may need to reset your account or unlock it on their end.

Frequently Asked Questions

Why does Teams keep sending me back to the login page?

This is called a sign-in loop. It almost always means a corrupted or expired login token is stored on your device. Clearing the Teams cache fixes it.

I know my password is correct — why won't Teams accept it?

Your account may be locked, or a conditional access policy from your company is blocking sign-in. Contact your IT helpdesk to check the account status.

Can I sign in to Teams without reinstalling it?

Yes. Clearing the cache and removing old credentials from Credential Manager usually fixes sign-in issues without needing to reinstall the app.