Apple has sent an email developers alerting them to the fact that certain older betas of iOS 8 and OS X Yosemite will no longer be able to take advantage of CloudKit functions like MailDrop, iCloud Photo Library, or iCloud Drive. This is likely due to an older sandbox server being taken offline as the operating systems come closer to reaching their public releases.
Developers who wish to keep testing against these features will need to update to at least beta 5 of each operating system. CloudKit and its various applications are part of iOS 8 and Yosemite, which will be required for all users who wish to use these functions when they are released later this fall.
Apple will unveil its next-generation iPhone 6 in just over two weeks. The two new devices are expected to ship with iOS 8 pre-installed.