Apple decided to sunset the private iTunes U sites which Columbia used to distribute content internally, usually protected using a UNI and a course affiliation.

Apple's statement: "As institutions have focused more on contributing content to the public catalog and building public and private courses with the iTunes U app on iPad or using Course Manager, fewer and fewer institutions are using the original iTunes U private sites for distributing their content internally. As a result, Apple will be discontinuing legacy iTunes U private sites on September 1, 2015." All content has been removed from the platform.