Hi There,
I think I just managed to solve a quite similar problem to this.
Situation:
- iPhone 5s, running on iOS 7.something and a new iPhone 6 on iOS 8.0.2
- iCloud was already updated to iCloud Drive, but no Backup of WhatsApp-Data has been done so far
- Did a full backup of the iPhone 5 onto my Mac, and restored then the backup to the new iPhone 6
- Everything was fine, besides of WhatsApp, telling me I have to reinstall it and then get all the Messages from the iCloud-Backup of WhatsApp
- Started a WhatsApp-Backup from the iPhone 5s to iCloud, but this stuck somewhere at 97% and stayed there for about 2h
Steps that helped me:
- Reinstalled WhatApp on the iPhone 6
- Logged into iCloud through System Preferences from a OS X 10.10 Mac, to delete the WhatsApp-Backup (only way to do this, no possibility through Webinterface or OS X 10.9.X)
- Reloaded the Backup onto iPhone 6, and as the welcome screen appeared, I skipped the Login to iCloud.
- Verified the new iPhone 6 with WhatsApp and voilà, all the messages where there.
- Did a new backup from the iPhone 6 WhatsApp-Data onto iCloud
What I don't know is:
- Was it only possible because I first reinstalled WhatsApp again on the iPhone 6
- As far as I can tell, the problem did not happen on a iPhone 5s which was already updated to iOS 8.0.2 and then moved to a iPhone 6
- Looks like the setup process of a new iOS8 device moves the iCloud to iCloudDrive, which then makes it unpossible for a iOS 7 device to send WhatsApp-Data onto it.
Hope this helps someone - let me know your experiences with that try.
Cheers,
Florian