winrt xaml - Speech to Text works fine on emulator but I get an error on phone -

winrt xaml - Speech to Text works fine on emulator but I get an error on phone -

i'm trying run code below runs fine on emulator operation not valid due current state of object. exception @ recognizewithuiasync() if run on device.

// compile dictation grammar await speechrecog.compileconstraintsasync(); // start recognition speechrecognitionresult speechrecognitionresult = await this.speechrecog.recognizewithuiasync(); // show output var sttdialog = new windows.ui.popups.messagedialog(speechrecognitionresult.text, "heard said..."); await sttdialog.showasync();

some additional info: method async; checked microphone permissions @ manifest file , have 4 voices installed on device.

winrt-xaml windows-phone-8.1