Dna testing

So.. the father of my unborn child walked out on us 2 months ago and is now claiming he wants a paternity test. He knows this is his child.. he’s being totally nasty to me. Besides the point... so I went a couple weeks ago and got the test done and today the results came back and he said they didn’t have enough fetal count to do the test? Does anyone know anything about this? I don’t understand what that means and he doesn’t seem to really know either.