YouTube Content ID is a great tool to monetize videos using your music, but there are some types of content that are unfortunately not eligible for it. Please note that this is determined by YouTube itself and MusicHub has no control over it. The following types of content and recordings cannot be selected for Content ID.
Non-exclusive content licensed from third parties
Cover versions
Unlicensed samples
Compilations, unless you have the express permission of all artists appearing on that compilation
Live recordings or recordings from concerts
Content released under Creative Commons or similar free/open licenses
Public domain recordings or compositions
Karaoke recordings, remasters, sound-alike recordings
So-called "royalty-free" music libraries, usually licensed for use in game, film, television or other soundtracks. (Production Music)
Meditation, yoga or sleep content
Content that is already monetized on Youtube through another distribution service
More information can be found here.