Although I have I have voice in all other applications , in cubase artist I have signal but no voice.I use Mac os mohave in an iMac27-inch, late 2012
My initial thought is that you have the track monitor function enabled. It should be enabled during recording and disabled during playback.
If that is not it, then you need to give more detail. Like screen shots of your VST connections input and output tabs and screens shots of the project window showing the inputs and outputs set in the inspector.
Regards 
where is the track monitor function?
anyway, I solved the voice problem with irig hd2 connected with electric guitar and headphones (functioning like external voice card) .
thank you