Google Working on an Issue With Google Home and Google Play Music
Google has acknowledged that they are working on a reasonably significant bug between Google Home and Google Play Music. The issue varies from user-to-user but most are experiencing one of two issues. First, purchased music is not showing up in their libraries and is not playable. Second, entire libraries for some artists are not searchable or playable. What makes it interesting is that if you open up the Google Play Music app and Cast the songs in question to Google Home, they will play.
The issue was discussed in detail in a post in the Google Product Forums for Google Home. There, users were encouraged to use the Send Feedback feature within the Home app to send detailed information to Google so they can continue to investigate. Right now, there isn’t a fix available.