I have 3 flow hives and they took virtually a year before the bees moved in.
Spraying with sugar water is a good way to get them in there.
If you scrape some wax off their brood box drop it into the super.
As for experienced beekeepers.
They all seem to rubbish the product.
"What the farmer don't know, he don't eat"
They all quote the plastic being bad, but they all use plastic foundation frames??
Its so easy to knock someone.
My flow frames are all well frequented now but they do take time.
Do read up on harvesting techniques on the forum.
DO NOT put the lever in all the way and take honey out. Do it in 1/4 depth at a time.