It's because you're trying to dial the skimmer in to skim with no bioload right now. I'd suggest setting the water level really low in the skimmer, about 1" below the connection where the cup meets the body and just leave it there for now. The skimmer will continue to break-in, and any little bump in organics for the time being will result in the skimmer height somewhat increasing and maybe building a little bit of a foam head.
Sounds like a good plan. Thanks, Jeremy!