Currently, the list of services affected includes: App Store, Apple Music, Apple TV, iBooks Store, iTunes in the Cloud, iTunes Match, iTunes Store, iTunes U, Mac App Store, OS X Software Update, Radio, and Volume Purchase Program.
According to Apple the issues began around 9:45 EST this morning.
All Store Services - Some users are affected
Users are experiencing a problem with the services listed above. We are investigating and will update the status as more information becomes available.
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