In general the options grey out if the add-in doesn’t understand the project type. I think MVC ASP.NET applications produce this, but things like COM+ apps and services will confuse it as well. (Which in a way is fair enough, as these have to be installed after compiling and ANTS can’t do that for you)
The solution I'm working in now contains 22 projects:
2 .NET EXE projects (one console, one WinForms)
1 VC++ Makefile project (used to automate a bunch of post-build stuff)
19 .NET DLL projects, of which 7 are VSTS unit test projects.
The Makefile project is the Startup Project in the solution.
If I remember, I'll try opening a solution that doesn't have a Makefile project in it to see if that's throwing it off (seems like the most likely candidate).