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If the Teams desktop application starts misbehaving (missing messages, errors, etc) a cache clear can often help.
Windows
- Quit (completely exit) Teams and Outlook. Make sure they are not still visible in the system tray.
- Open File Explorer
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- Open the Teams AppData folder: Enter %AppData%\Microsoft\Teams\ in the address bar, and press Enter
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- Delete all the contents of the Teams AppData folder
- Re-open Teams and Outlook
macOS
- Right-click the Microsoft Teams icon in your dock, then select Quit
- Open Finder and select Go > Go to Folder
- Copy and paste the following into the Go to Folder box, then select Go
~/Library/Application Support/Microsoft
- Right-click on the Teams folder and select Move to Trash
- Click the magnifying glass in the upper-right corner of the screen to open Spotlight Search
- Enter 'keychain' in the search bar and select Keychain Access in the search results
- Within Keychain Access, search for 'Microsoft Teams' and locate the "Microsoft Teams Identities Cache" entry
- Right-click and select the option to Delete the entry
- Close Keychain Access
- Relaunch Microsoft Teams. You may be prompted for sign-in credentials.
Linux
https://gist.github.com/mrcomoraes/c83a2745ef8b73f9530f2ec0433772b7