Hi Atomicsynth,
first of all I recommend that you take out ‘C:\Program Files\Native Instruments\VSTPlugins 64 bit’ again from the pathlist in the preferences dialog. Why is that so?
Kontakt 6 now also comes as VST3 plug-in and those Dorico finds automatically without specifying a path, because VST3 plug-ins reside in specified paths. Kontakt 6 gets installed in both, VST2 and VST3 flavours, but since VST3 is there, you better “hide” the VST2 version from Dorico in order not to “confuse” it, so that it is clear that it only ever loads the VST3 version.
Now to the not sounding Kontakt. From the log files I can’t see the reason for it. Send me a mail to ‘u dot stoermer at steinberg dot de’ and we can arrange a remote session where we can have a look together.