I recently Installed AutoCAD 2021, and when clicked on the Vault tab, I noticed that the tab was blank.
The fix is pretty simple, even if seemingly scary. This problem occurs when the Vault client is installed before AutoCAD.
Make sure that AutoCAD is not running.
From the Windows “Add Remove” programs, find “Vault Client 2021” (Professional in my case). Then select “Uninstall”- Don’t worry, we’re not actually uninstalling it!
The Uninstall Wizard will start up, click “Add or Remove Features”.
Select “AutoCAD 2021 Add-in”, then “Update”
The installer will update, click “Finish”
Fire up AutoCAD, open a file and the “Vault” tab should be back to normal.