Hey everyone, that is a common problem that I myself was stumped with until someone helped me out.
The problem is that wav2 lip doesn't work if the directory structure has any spaces in it.
For instance, c:\desktop\wave 2 lip \ will mean that wav2 lip will, frustratingly, not work.
However, c:\wav2lip or some variant of, should yeild positive results. Remember, no spaces.
Hopefully that will help!
Regards
Zahael