Teams freezing on the loading screen or refusing to launch is usually a stuck process or a corrupt cache, not a broken install. These steps go from the 10-second fix to the full reset.
A corrupt cache is the classic “stuck on the loading screen” cause. Clearing it is safe. Your chats and files live on the server, not in the cache.
%appdata%\Microsoft\Teams and press Enter (classic Teams). For the new Teams, clear the cache under %localappdata%\Packages\MSTeams_8wekyb3d8bbwe\LocalCache.KoalaFix does this triage for the person who just wants Teams to open: it ends the stuck processes, clears the right cache for whichever Teams you’re on, and reinstalls if it has to, all from “Teams won’t open.” No ticket, no hunting through AppData.
Almost always a corrupt cache or a background Teams process that never closed. Quit Teams fully, clear the cache, and relaunch.
Quit Teams, then delete the contents of %appdata%\Microsoft\Teams (classic) or the new Teams LocalCache folder, and reopen Teams.
Yes. The cache only stores temporary data and rebuilds on next launch. Your chats, files and meetings are stored on Microsoft’s servers, so you won’t lose anything.