By Clint Brown
I was asked about missing Vault add-ins for AutoCAD 2016 by a customer. In this specific instance their Vault ribbon had seemingly disappeared for no reason.
We fixed the issue by unloading and then loading the Vault CUI customisation and the ribbon now displays as expected.
Below is a short video outlining the steps required.
Autodesk have also documented this fix in the following article. They also have some other suggestions that you can try if the CUI fix above does not work on your system.