Are you saying “I had only one brood box”? Just trying to make proper sentence of your first sentence.
You could try it, but you can never tell with bees what they will do. I understand that most of Hawaii is tropical, and therefore has year-round nectar flows, but in the more northern climates, at this time of year bees can be very reluctant to cap honey. With that in mind, I would probably just extract your super the traditional way, and try again with the Flow super.
Did you prepare the Flow super at all? Did you put any wax or burr comb on it before putting it on top of the brood box? If not, that may be why they ignored it. 