In my Case, i had to accept the Apple Developer License Agreement.
Login to apple developer account and observe the notification message similar to below.
"The Apple Developer Program License Agreement has been updated. In order to access certain membership resources,**** must accept the latest license agreement by June 28, 2016."
Earlier, i was not able to add/edit iCloud Containers to the App ID though i changed/checked Capabilities, Provisioning Profiles, Certificates etc. After agreement to the contract, things started working smoothly.
Hopefully, it would save someone's valuable time.