I am using an iMac OS 10.13.6 and until recently had experienced no problems adding downloaded music files to my Audirvana library.
Recently I have been unable to sync with my Users/Home/Music folder and my iTunes playlist.
This may or may not be related to the fact that I recently switched to DSD files (converted from PCM downloads).
I was able to download one DSD file - Exile On Main Street by the Rolling Stones - on Dec. 27 but had no luck a couple days later when I tried to sync Audirvana with a few more DSD files.
Progress bars seemed to indicate successful syncs with my iTunes playlist and my Music folder but album images do not appear in my Audirvana Library.
Tried everything I could think of with no results. FWIW I upgraded to the latest software version and that didn’t fix the issue.