Currently, there is no definitive fix from Microsoft. The temporary workaround is to manually trigger the synchronization via SharePoint.

Follow the steps below:

1. Go to the relevant channel in Teams.
2. Click at the top on “Open in SharePoint” (or open the underlying SharePoint site directly).
3. Go to the “In channel library” (the channel’s document library).
4. Open a few folders.
5. Click around in the different subfolders.
6. Wait a moment so that synchronization restarts in the background.
7. Then go back to Teams, log out, and reopen the “Shared” tab.
8. In most cases, the tab will work correctly again afterward.

In most cases, these steps should fix the issue.