Continuing mail and iCloud problems

Further to my earlier posts, my me.com & iCloud.com emails are no longer received on my iPad. (I can send from the account via the iPad.) Also keychain keeps telling me it's pending, and when I try to activate it with a security code, that never arrives on my phone, though it's clear that the phone number is correct. This all began after the iOS 8.3 update. I have now backed up and restored the iPad twice, and repeatedly signed out of the account, switched off the iPad and signed in again. I have also visited an Apple Store where those were the only suggestions. I thought I had cracked it after seeing a suggestion in the forums to wait... Four emails came in, but have since disappeared. The young man at the Apple Store suggested that it is a software problem and waiting for Apple to issue an update is my only option.

Has anyone any idea when that might be?

The problem is at the least a huge inconvenience, and any help would be very much appreciated.