Recently I experienced issues with iWorks apps (Keynote, Numbers and Pages) synchronising across iOS devices and Macs. Even moving files out of iCloud Drive and re-uploading only one file, the issue persisted.
There is a solution to resolving this, however it may be possible that data will be lost if the following is carried out on older versions. The issue appears to be related to a synching failure with the files, to resolve this I opened each file and made a little change. Once completed I reactivated iCloud Drive across my iOS devices and all synchronised the files quickly.
The exact cause of this issue is unknown at the moment and I will continue to monitor to see if it occurs again.
UPDATE. This issue has been resolved with the recent Yosemite update. However the following is beneficial if you have not updated or are still experiencing issues.
Recently I noticed that when mirroring my computer to my AppleTV, that I was unable to browse the internet. Once disconnecting AirPlay WiFi was back up and running. After some searching I have found the following.