Make sure you have the latest version of Vizard 5 by going to Help > Check for Updates. Then try adding the following code in the postInit section of the vizconnect file:
Code:
import steamvr
hmd = steamvr.getExtension().getHMDList()[0]
hmd.setMonoMirror(True)
Do you still get an error? If so, please attach your vizconnect file here.