Hi @IBN ,
From your description, do you mean when the user logged in the Teams client, the status always showed as "offline" and no messages can be sent or received?
In order to help narrow down the issue, please check it from the Teams web client via https://teams.microsoft.com and see how it goes. If it works fine in Teams web app, then please sign out and then sign in again in the Teams desktop client and check the result.
In case it still doesn't work, please try clearing the Teams client cache and see if there would be any improvement:
- Sign out and then quit the Teams desktop client.
- Navigate to C:\Users\<UserName>\AppData\Roaming\Microsoft\Teams
(Note: The AppData folder may be hidden, in this case, please go to View on the ribbon, then tick the "Show Hidden folders" box.)
- Delete all the content from this folder.
- Restart Microsoft Teams.
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