The GUID is only part of the issue.

Per your Screen Caps, you're using 2015 CADmep and 2016 Revit.

Which configurations are available are stored on a "per version" basis.

So 2015 looks in the 2015 section of the registry to see which databases are available. 2016 looks in the 2016 section of the registry. 

Easiest way to fix this if you're not comfortable editing the registry is to launch CADmep 2016 and add/browse to your configuration. That'll att it to the proper section of the registry and Revit 2016 will then see it.