iTunes Store Doesn't Recognize iTunes Library

About two weeks ago, iTunes stopped recognizing my iTunes library. I get this message when I go to either File → Library → Update iCloud Music Library or Update Genius:

There is no such option under File → Library. I tried disabling Genius Recommendations under my account, then turning them back on, but with no success. What is causing this and how can I fix it?

I have iTunes Match, but not Apple Music, if that matters.

Solution 1:

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.