This problem happens intermittently for different libraries and different projects. When trying to import a library, the package will be recognized, but the class name can\'
@Anton Dozortsev I was driven crazy by a similar behavior; I ended up re-installing the IDE a bunch of times, only getting past the issue after removing the IDEA app, all caches, preferences, etc.
I tried all kinds of steps in the interim, (like restarts, invalidations, deleting .idea and *.iml files, and others.)
Turns out, the problem was due to IntelliJ's idea.max.intellisense.filesize setting. I had set it to 100KB, which was smaller than my dependency's size, leading to IntelliJ showing it as unknown, just like in your screenshot.
Fix:
Click on Help -> Edit Custom Properties
Set the property to a larger value; the default is 2500KB
idea.max.intellisense.filesize=2500