I can't turn on iCloud backup on my iPad Air2.

I 'm not able to change my iPad backup location from my home iTunes Mac computer to my iCloud account. The settings choices under my iCloud setting with the current iOS 8.3 software do not allow me to choose to backup to the iCloud. The slide switch to turn it on is greyed out and can't be accessed. My iTunes account settings will tell me I'm not logged into my Apple ID account when I really am. All my other Apple devices like iPhones, iTouches, mini iPads, etc will all backup to the Cloud just not my newest iPad Air 2.