I tried adding Electric Sunburst and Evolution Infinity to Kontakt and I always get this message. I also tried using the old KLC tool but it doesn't help. Those 2 libraries do show up in Kontakt after using KLC but it still asks me to locate the folders with instruments. Well, when I locate them it still doesn't work, after clicking .nki file it tells me to add library first, which I can't do...

I'm just lost at this point. I tried removing both libraries through Regedit and re-adding them but still, I get the "Library not found".

 

I think this is a classic problem.

Have you tried to remove possible .xml files in the Native Instruments folder? You may have to do this in addition to remove the reg entries.

Or perhaps you didn't enter the correct path when you used KLC. The instruments folder should appear.

Anyway, if the libs come with their own .nicnt files you shouldn't use KLC or equivalents (IDK if it's the case).