The other songs work fine but that one says "This song is not available. If you have the file on your computer you can import it" Spotify URL: spotify:track:5noCg9XIxCozI01ZTUvtq8 Clavicula Nox - Therion
Thanks for getting in touch. Just to expand on @Ryythrin's post - we'd love to have all the world’s music on Spotify. Hopefully we'll have this song back in the future. There's info about Spotify content here.