Sorry to hear that. I had that happen too, even when I had a broody sitting on them. I didn't float test but it was super humid around hatch time and I think they drowned. It is so sad seeing those little lost lives end even before they've started.
Last hatch I had one fully developed chick, yolk sack absorbed and everything...just never attempted the pip, when I opened it it was gone. It's so sad sorry for your chicks.