Most likely, it's the timing. You can HC into Slide, Clone, or Freeze. I can Hit Confirm all day in practice, but online, it's difficult. Hit Confirming the F4 is rather tight, but with enough space to get it. I don't even use it online, unless I know for a fact it's going to hit.
Best of luck to ya.
~Hound.
EDIT: I agree with Donix, I almost never go online.