Build Project hammer greyed out?

[soundhound]

anyone know what causes the hammer symbol representing 'Build Project' to grey out for a currently selected project?
'Build Project' is still available on a right button menu and from the Project menu at the top, but they don't do anything.

I can xmake at the console successfully and then xrun bin/...
but back in xtc, it doesn't seem to think there is a binary to run ('Binary not found')
help!

[andrewxcav]

Is it still grayed out if the file containing main() is in focus on the editor pane? I have found that even when "Setting current project" sometimes Eclipse can get confused.