I installed on a new desktop VS 2012 and VS 2015 and ArcGIS 10.4 and when I open VS 2012 or VS 2015 the option "Add ArcGIs reference" does not show on the menu, so I can not add a reference to a GIS library. See attached print screen from another computer where this option it shows.
Also all Esri references appear in Red.
It only happens when I open a VS web site, if I open a VS project it works fine.
What am I missing?