Nothing new on this at all? This is a major problem for my use of Dorico 3, as all my orchestral libs have been resaved to Kontakt 6 format. 
Any potential tips on solving this would be greatly appreciated. I had the same issue with Cubase blacklisting Kontakt, but here it was a simple case of adding it to the whitelist. That doesn’t seem to do anything at all in Dorico.
Sorry Jesper, just saw your posting now. Could you please attach a diagnostic report here, so I can first get an overview?
Thanks for the data. Very strange that Kontakt 6 gets blacklisted. Please try following:
Navigate to C:/Users/Jesper/AppData/Roaming/Steinberg/VSTAudioEngine3_64
and delete the two files ‘Vst2xPlugin Blacklist VSTAudioEngine3.xml’ and ‘Vst2xPlugin Infos VSTAudioEngine3.xml’
and then restart Dorico. That will trigger a rescan of all VST2 plug-ins.
Because once a plug-in is on the blacklist, it won’t get scanned anymore.
So chances are, that then Kontakt 6 will get recognized, because as you wrote, manually invoking the scanner does produce the expected output.
If it still gets blacklisted, please create a new diagnostic report.
No dice. I have actually tried that already, but gave it another go now, unfortunately with no luck still. I cannot attach the new diagnostic report because it is too large (2.28 MB).
I have also tried removing the whole VSTAudioEngine3_64 folder, also without it fixing the issue.
There is a Memory Dump File in the Crash folder in the report, is that a clue?
Why did you remove the crashes folder? Please leave it in.
See above. File too large to attach with the crashes folder included.
Another thought, is that Kontakt.dll the real file, or is it maybe only a symbolic link? Our scanner has problems following symbolic links.
It is the real file, not a symlink.
And just the crashes folder zipped up is also too large?
Ah, no. That was just me being dumb. 
I have attached the report with only the crashes folder in it.
Dorico Diagnostics.zip (1.42 MB)
Ah, thanks. The crash is from the audio engine, but it has nothing to do with Kontakt getting blacklisted. I’m still don’t know what to suggest further. I guess I need a good night sleep over it…
I had another look at the XML files and noticed something. The VST2 Search Paths shows as first and last path
C:\Program Files\Steinberg\Vstplugins
C:\Program Files\Steinberg\VSTPlugins\Native Instruments
Is maybe a double scanning an issue? I’m just speculating. Already with the first search path every subfolder in Vstplugins shall get scanned. Then the last path points to one of the already scanned subfolders. Could be that the scanner gets confused by that. Could you try with taking out the last search path? (And also delete the blacklist again)
Coming back to what I just wrote before, can you please check in C:\Program Files\Steinberg, is there really only one folder VSTPlugins or is there a second one Vstplugins? Normally Windows would treat both names same but maybe that’s different on your machine…
I tried removing the C:\Program Files\Steinberg\VSTPlugins\Native Instruments from the VST2 search path and restarting Dorico. No luck with that, unfortunately. Also, there is only a single VSTPlugins folder present.
As mentioned in an earlier post, the weird thing is that Cubase 10.5 actually also blacklists Kontakt 6 (Kontakt.dll), but here adding it to the whitelist solves the issue. This does nothing for Dorico, unfortunately.
I will need to discuss this tomorrow with the guy who wrote the vstscanner. And will also get a trial installation of Kontakt 6 and see how that behaves with me. I’ll be back…
I have not experienced a difficulty using Kontakt 6; I did note that the new version merely appears as “Kontakt” without a number (and thus overwrote the subsequently superfluous Kontakt Player) which may cause some confusion.
[Attachment deleted by the admin because it showed the serial number of Kontakt]
I’ve not had a chance to talk to Mr Vstscanner as he is not in today, but I just installed Kontakt 6 Player to my laptop and had no issue at all with getting it going. Just installed via Native Access, then set the path to Kontakt and it was immediately recognized by both, Dorico and Cubase.
Jesper, what exact version of Dorico and Cubase do you have?
Found on the Native website following page: https://support.native-instruments.com/hc/en-us/community/posts/360006981157-Cubase-elements-10-Blacklists-Kontakt-and-Komplete-Kontrol-en-us-
What if you follow those instructions, do you at least get it to work with Cubase again?