Got it to work. The only way I got it to work is to launch from command line. ex: gammaray --probe PROBE_OF_CHOICE PATH_TO_QT_EXE\qt_app.exe.
And of course the probe config must be the same as the app's build config. For reference, my environment is Windows 10. GammaRay on Qt 5.6 QtQuick 2.0 apps.