Microsoft Teams sign-in errors: "We couldn't sign you in" and CAA codes

When Microsoft Teams can't log you in, it shows a message such as "We couldn't sign you in. Please try again." and, in the desktop app, a status code. Microsoft says the code appears in the bottom-left corner of the sign-in window and exists to help an IT admin work out what failed. The codes start with CAA, written in full as 0xCAA70004 and so on.

Some codes you can fix yourself in a minute, such as a wrong clock or a dropped connection. Others point at your organisation's sign-in rules, and only an admin can change those. The list below is Microsoft's own.

Is Teams down?

Check our Microsoft Teams status page for live checks and reports from other users. Microsoft also has a public service status page at status.cloud.microsoft, meant for times when people can't sign in at all. If colleagues in your organisation can sign in normally and you can't, it isn't an outage: go to the codes below.

What each status code means

• 0xCAA20003: an authorisation problem. Microsoft's fix is to check that your device's date and time are correct, because a wrong clock stops secure connections working.
• 0xCAA20004: your sign-in needs approval from your organisation's sign-in system. Microsoft says this happens when a conditional access policy is involved, for example rules about which devices or locations may sign in. Your IT admin has to check the organisation's Microsoft Entra ID policies.
• 0xCAA70004: the server or proxy wasn't found. Usually a proxy is set up wrongly, or a tool that inspects network traffic is running. On a work computer, tell IT. On your own computer, turn off any proxy or VPN and restart Teams.
• 0xCAA70007: the connection was interrupted. Check your internet connection. If it's fine, a firewall or another app may be blocking Teams.
• 0xCAA82EE2: the request timed out. Check your internet connection, then check nothing is blocking Teams.
• 0xCAA82EE7: the server name couldn't be resolved. Teams couldn't look up Microsoft's address, which is a connection or DNS problem. Same checks as the two codes above.
• 0xCAA90018: wrong credentials. Microsoft explains that the account you used to sign in to Windows is different from your Microsoft 365 account, and Teams tried the wrong one. Sign in again with the correct work email address and password.
• No code, on a computer with a smart card: the smart card PIN needs entering again. Take the card out and put it back in.

Fixes you can try yourself

1. Set the date and time to automatic. On Windows: Settings, Time & language, Date & time, then turn on Set time automatically. This is Microsoft's fix for 0xCAA20003.
2. Sign in on the web at teams.microsoft.com. If that works, your account is fine and the desktop app is the problem. You can also carry on working there.
3. Check your connection. Turn off any VPN or proxy, or switch to another network such as a phone hotspot. The timeout and name codes (82EE2, 82EE7, 70007) are all connection failures.
4. Update Teams. Open the Settings and more menu next to your profile picture and choose Check for updates. If you can't get that far, restart the computer so any waiting update installs.
5. Quit Teams completely and reopen it. On Windows, right-click the Teams icon near the clock and choose Quit.
6. Reinstall Teams if the error survives all of that. Microsoft lists this as the last manual step.
7. Send the code to your IT admin. Microsoft's advice for any code you can't clear is to note it and pass it on, because many of them can only be resolved by an admin.

Work or school account, or personal account?

Teams has two kinds of account and they don't mix. A work or school account belongs to an organisation, which controls who can sign in and from where. A personal Microsoft account (for example an outlook.com or hotmail.com address) signs in to the free personal version of Teams. Entering a personal address when you meant your work one, or the other way round, is a common reason for a sign-in that keeps failing. Check which address the sign-in box is showing before you retype the password. The CAA codes and the advice to contact an admin apply to work and school accounts. With a personal account there's no admin, so the device fixes above are the ones to use.

For IT admins

Start with the Service health page in the Microsoft 365 admin centre: in the left-hand menu go to Health, then Service health. The Overview tab shows current incidents and advisories for Teams, and Report an issue lets you tell Microsoft about a problem that isn't listed. Microsoft also provides a Teams Sign-in diagnostic in the admin centre, which tests a named user's account, and a Teams sign-in test in the Microsoft Remote Connectivity Analyzer. For 0xCAA20004, review the conditional access policies that apply to Teams.

Three places the fault can be

• Microsoft: many organisations are affected at once, the web version fails too, and the Service health page or Microsoft's public status page shows an incident. Wait. Reinstalling won't help.
• Your organisation: you can reach the sign-in page and your password is accepted, but access is refused, often with 0xCAA20004. Typical triggers are a new or unmanaged device, signing in from abroad, an expired password, or a licence that was removed. Only your admin can see which rule applied.
• Your device or network: colleagues are fine, Teams on the web works for you, and only the desktop app fails. Clock, proxy, VPN, firewall or a damaged app are the usual causes.

Why the clock matters

Signing in to Teams means exchanging security tokens that are valid for a limited time. If your computer's clock is wrong by more than a few minutes, the tokens look expired or not yet valid, and the sign-in is rejected even though your password is correct. This often happens after a laptop battery has run completely flat, or after travelling when the time zone was changed by hand. Setting the time to automatic fixes it.

What not to do

Don't keep retyping your password. Organisations commonly lock an account after several failed attempts, which turns a small problem into a call to the helpdesk. Don't give your password or a verification code to anyone who contacts you offering to fix Teams: real IT staff don't need them. And don't delete your account from the device as a first step, since on a work laptop that can remove access to other Microsoft 365 apps too.

What to tell your IT admin

Give them the exact status code, the time it happened, whether Teams on the web works, and whether you were at home, in the office or on a VPN. Microsoft asks admins for the same details when they open a support request, so having them ready shortens the wait.

Related fix guides

• Zoom error codes explained, and how to fix them
• Outlook not receiving emails: how to fix it
• How to fix ERR_CONNECTION_TIMED_OUT
• DNS server not responding: how to fix it