Fixes / Teams · Checked September 30, 2026

Teams error code 80080300: what it means and how to fix it

Short answer

Error code 80080300 means the Teams desktop app could not finish starting up or signing you in. The usual cause is damaged local app data, not your account. Quit Teams fully, clear its cache (in new Teams on Windows, go to Settings > Apps > Installed apps > Microsoft Teams > Advanced options > Reset), then open Teams and sign in again.

What this message means

80080300 is a startup and sign-in failure in the Teams desktop app. It usually comes with the message "We're sorry - we've run into an issue". Teams could not load its saved sign-in state or its local files, so it stops before it opens your chats. Your account, password and Microsoft 365 licence are usually fine. A quick way to confirm this is to sign in at teams.microsoft.com in a browser. If that works, the problem is only the app on this computer, and you can fix it by clearing the cache, removing saved credentials, updating the app or reinstalling it.

Common causes

Cause	How to tell
Corrupted Teams cache or local app data	Teams in the browser (teams.microsoft.com) signs in normally, but the desktop app shows 80080300 every time it opens, even after a restart.
Stale or conflicting saved sign-in credentials in Windows	The error started after a password change or MFA reset, or after you added a second account (for example a personal and a work account). Credential Manager lists old entries with "msteams" or "MicrosoftAccount:user=" in the name.
Outdated Teams build clashing with a recent Windows update	The error began right after a Windows update or a Windows 11 upgrade, and the Teams version is old (you may still be on classic Teams, which Microsoft has retired).
Broken or incomplete Teams installation	Clearing the cache does not help, Teams crashes or hangs before the sign-in window appears, or the Sign out option does nothing.
Problem with the Windows user profile	A clean reinstall still fails, but Teams signs in fine when you log in to Windows as a different user on the same PC.

How to fix it

1. Reset new Teams on Windows (clears the cache)

New Teams on Windows 10 and Windows 11

Right-click the Teams icon in the taskbar notification area and select Quit, so Teams is not running in the background.
Open the Settings app and go to Apps > Installed apps (on Windows 10: Apps > Apps & features).
Search for Microsoft Teams, select the three dots (...) next to it, then select Advanced options.
Under Reset, select Reset. This deletes local app data and your personal Teams settings, but not your chats or files, which are stored online.
Open Teams again and sign in. The first start after a reset can take longer than usual.

2. Delete the Teams cache folder manually

Windows (new and classic Teams) and Mac

Quit Teams completely (Windows: right-click the taskbar icon > Quit. Mac: press Command-Q).
Windows, new Teams: press Windows key + R, paste %userprofile%\appdata\local\Packages\MSTeams_8wekyb3d8bbwe\LocalCache\Microsoft\MSTeams and press Enter.
Windows, classic Teams: press Windows key + R, paste %appdata%\Microsoft\Teams and press Enter.
Delete everything inside the folder that opens, then restart Teams.
Mac, new Teams: open Terminal and run rm -rf ~/Library/Group\ Containers/UBF8T346G9.com.microsoft.teams and then rm -rf ~/Library/Containers/com.microsoft.teams2, then reopen Teams.

3. Remove saved Teams credentials from Credential Manager

Windows 10 and Windows 11

Quit Teams from the taskbar icon.
Open Control Panel > User Accounts > Credential Manager, then select Windows Credentials.
Under Generic Credentials, expand and select Remove on each entry whose name contains "msteams" or "MicrosoftAccount:user=" for the affected account.
Restart the PC, open Teams and sign in with your work or school address.

4. Update Teams, or move off classic Teams

Sign in at https://teams.microsoft.com in Edge or Chrome to confirm your account works.
If the desktop app opens far enough to show your profile picture, select Settings and more (...) > Check for updates.
If you are still on classic Teams (purple icon, no "New" label), install new Teams from https://www.microsoft.com/microsoft-teams/download-app, because classic Teams no longer receives fixes.
Restart the computer and try signing in again.

5. Run classic Teams in Windows 8 compatibility mode

Classic Teams on Windows 10 and 11 only. New Teams is a Store-style app and has no Compatibility tab.

Quit Teams from the taskbar icon.
Right-click the Teams desktop shortcut and select Properties (on Windows 11, select Show more options first).
Open the Compatibility tab and tick Run this program in compatibility mode for.
Choose Windows 8 from the list, select Apply, then OK.
Open Teams and sign in. Treat this as a stopgap and move to new Teams when you can.

6. Clean reinstall of Teams

Uninstall Microsoft Teams (and Teams Machine-Wide Installer, if listed) from Settings > Apps > Installed apps.
For classic Teams, press Windows key + R, open %appdata%\Microsoft and delete the Teams folder.
Restart the PC.
Download Teams from https://www.microsoft.com/microsoft-teams/download-app, right-click the installer and select Run as administrator.
Sign in. If it still fails, sign in to Windows as a different user and test there to rule out a damaged Windows profile.

Next time, skip the search

Crade is an AI assistant for Mac and Windows that sees your screen. When a message like this pops up, ask “what does this mean?” and it explains the exact error in front of you, step by step.

Download Crade

Still not fixed?

Use Teams in a browser at teams.microsoft.com while you keep troubleshooting. If you have a work or school account, contact your IT department and give them the exact error code. They can run the Teams Sign-in diagnostic in the Microsoft 365 admin center, run the Teams Sign in test at testconnectivity.microsoft.com, and collect Teams debug logs for a Microsoft support request. For a personal Microsoft account, contact Microsoft Support through the Get Help app in Windows.

Questions people ask

Does error 80080300 mean my account is blocked or my password is wrong?

Usually not. If you can sign in at teams.microsoft.com in a browser, your account is fine and the problem is the desktop app on that computer.

Will clearing the Teams cache delete my chats or files?

No. Chats, files and meetings are stored in Microsoft 365 and download again when you sign in. You only lose local settings such as theme and notification preferences, and the first start is slower.

Why does the Windows 8 compatibility mode fix sometimes work?

Some older classic Teams builds failed on newer Windows releases, and compatibility mode avoided the clash. It only applies to classic Teams. The lasting fix is to install new Teams.

Can having a personal and a work account in Teams cause 80080300?

Yes, some users hit it when switching between or adding accounts. Removing the old Teams entries in Credential Manager and signing in with one account first usually clears it.

Does 80080300 happen on Mac?

It is reported mostly on Windows. If a Mac shows it, quit Teams with Command-Q, delete the Teams container folders listed above in Terminal, and sign in again.

Sources

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