Ah, yes this happens to me quite a lot. You need to press it only once, then just go and do something else until it pops up, if you keep pressing the icon, for some reason, it will not come up(it gets irritated). It does this randomly. Just a glitch, nothing to worry about. If you try and quit FH after it does not come up, it will not work, in fact it will freeze, and you got to restart your computer, or shut down then turn it back on.
So the easy fix is to re download, although, this will probably happen again, at random times. It is a glitch, which is rather annoying. Sorry bout this dear ^^ You cant do much bout it though! Just be patient!
If you need anything else just ask, i specialize in mac sturff.. because i have one. Im always here to help c: