Audio windows speech GrammarRecognizer doesnt work?

Does someone know if there is a problem with the Windows speech GrammarRecognizer?
It does not run for me. All other speech stuff is running well.
On a Visual Studio c# native application it does work but in unity it doesnt.

Code (CSharp):

1.                 string ppath = Application.streamingAssetsPath + "/" + SRGSFileName;
2.                 grammarRecognizer = new GrammarRecognizer(ppath);
3.                 grammarRecognizer.OnPhraseRecognized += GrammarRecognizer_OnPhraseRecognized;
4.                 grammarRecognizer.Start();