FYI, after emailing Sonic Couture support about this issue, I received a prompt reply with possible fixes.
Simply deleting the "NativeAccess.xml" and re-launching Kontakt got my third party libraries (including Hammersmith Pro) back. If you have already installed v5.6.5, try it and see if it fixes for you. Also, as noted in the following email from SC support downgrading to an earlier installer should work as well. I was pleasantly surprised to get such a quick repsonse back and on a Saturday no doubt! Kudos to Sonic Couture! 
 
Hi Billy,

 
We’re working with NI on a proper fix, but in the meantime, please try the following:
 
1) Close Kontakt
2) Navigate the following directory and delete the file called NativeAccess.xml:
 
Mac: Macintosh HD / Library / Application Support / Native Instruments / Service Center
PC: C:/ Program Files / Common Files / Native Instruments / Service Center
 
3) Relaunch Kontakt - hopefully this fixes the problem!
 
If this doesn’t fix the issue, you can downgrade Kontakt back to your last working version. If you log into your Native Instruments account, you should be able to find a download of Kontakt 5.5.2, which is all that our instruments require (as opposed to 5.6.5 which is the latest problematic version). You can of course revert to Kontakt 5.6, if you prefer, which seems to work with no issues. 
 
Here’s the link to the older installers: https://www.native-instruments.com/en/support/downloads/update-manager/?search=kontakt
 
Please let us know if you keep having problems, and we’ll get in touch when there’s an official Kontakt fix from NI.
 
Thanks for your patience!



Regards,

Eddie
Soniccouture