Using the YouTube API, Soundiiz can only retrieve your "liked" songs from YouTube Music. That means we cannot retrieve "Library tracks" YouTube Music.
Also, due to the merge of YouTube and YouTube Music, we may be listing also liked videos from YouTube. Be sure to connect "YouTube Music" on Soundiiz if you want audio-only videos, and also, connect to the right "channel".
Be sure to enable "Show your liked music from YouTube" in YouTube Music if you want Soundiiz to retrieve your liked videos from YouTube: