iTunes Store Doesn't Recognize iTunes Library
Logging out of my iTunes account and logging back in did the trick.


Account → Sign Out
iTunes → Quit iTunes
Wait a bit, relaunch iTunes
Account → Sign In
iTunes → Preferences → General → uncheck iCloud Music Library
Click OK, wait a bit
iTunes → Preferences → General → check iCloud Music Library


iTunes should immediately start updating your iCloud Music Library. Once that’s done, everything should be working correctly.