I second what Dave has said here and offer an additional troubleshoot:
Whenever I fill a nova I quit filling when I reach the bottom of the little white silicon head cover. I have tried filling them all the way and find this tends to flood the coil. If you have completely filled though, just empty some out and then try it. It might takes 20 or 30 drags to unflood it.
Also, when I refill, it is not uncommon for the first 8-10 drags to be either no vapor or low vapor, but after a bit I can fog the room up. I think it's a matter of not flooding the coil.
Good luck.