It maybe your computer is not in idle mode.
The desktop client update itself automatically. Teams checks for updates every few hours behind the scenes, downloads it, and then waits for the computer to be idle before silently installing the update. Sometime new feature may not update to users in time. If you met this question, you could try to manually download updates by clicking Check for updates on the Profile drop-down menu on the top right of the app. If an update is available, it will be downloaded and silently installed when the computer is idle.
For more details about Teams update process, you could also refer to this article.
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