I first had this problem in Ableton and I reported it to Ableton, because all of my other VST3 plugins show up in the menu. Not a folder location issue - they all show up except Reaktor 6. Then I decided to use the Maschine software to create the loops I was wanting to do in Reaktor, and ****** the Reaktor 6 VST3 does not show up there either! When I click to load the plugin, if I choose Native Instruments/VST3, the whole list is visible EXCEPT Reaktor 6. If I try VST2 instead, I can see Reaktor 6 and load it. I have verified that the Reaktor 6 plugin is present in the VST3 folder (see screenshot).