Hi @IBN
Welcome to Q&A forum!
Before troubleshooting your problem, I have some questions to confirm with you.
A user is getting this error when trying to download file on Teams Chat.
What is this user's identity? Member or Guest?
Could this user upload/share the file to other users?
Could this user open this file normally in Teams client?
Can this problem be reproduced in Teams web client?
Does anyone else have the same problem in your organization?
If this question is only happened in the specific user, please try to clear Teams client cache and restart Teams client by following these steps to see if it can be fixed:
- close MS Teams, ensure it's not still running in the toolbar at the bottom right of Windows.
- navigate to %appdata%/Microsoft/Teams via File Explorer.
- select everything in the folder and delete it
- now open Teams again and it will download the data again.
Meanwhile, if you cannot open the file in Teams chat, try to use this article's resolution to see if works.
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