your iCloud music library session has expired?

Try Account -> Sign Out in the menu bar. Then Account -> Sign In to sign back in (I got a separate error message but otherwise seems to have worked). Evidently, this got moved in some later version of iTunes as I couldn't find it under the iTunes preferences window.

I was suffering through that popup for a few weeks as well. No idea really why it started popping up either, but it's incredibly annoying. I tried restarting iTunes, signing in and out of iCloud via System Preferences, restarting my computer, and updating OS X (10.11.6) and iTunes (12.5.5.5) followed by a reboot, but it still popped up! I've seen other suggestions to disable Apple Music, but I only have a single setting Show Apple Music Features that I can toggle on and off under Preferences -> General and didn't seem to fix the problem.

Hi, HUDHUD786.

Thank you for the question! It sounds like you are repeatedly receiving an alert that your iCloud Music library session has expired. I would recommend signing out of iTunes Store on your computer and then sign back in. I am not sure if you are using Windows or a Mac, but will include the steps for both.

iTunes 12 for Windows: Manage your iTunes Store account

iTunes 12 for Mac: Manage your iTunes Store account

Please let us know if the issue continues and thank you for visiting Apple Support Communities.

Cheers

Signing in and out did NOT work.

iCloud Music Library Session expired keeps appearing! Yet, we've never, ever signed up for or used Apple Music or iCloud!

Your solution worked for two days. The problem has reasserted itself. The window has appeared twice in the last ten minutes.

This sort of glitch is exactly the sort of thing that has me using Amazon more and more...Please, Apple, don't make me defect.