One some of the 9.1 beta versions one could not do a clean install of the phone and activate Whatsapp. It would keep giving an error that said the app had to be updated to the latest versions when it was already updated. The error would appear when putting in your phone number for the first time and waiting for the activation code. You could still use Whatsapp on 9.1 if you restored iOS from a backup, OTA updated, or option-updated the IPSW. Example: http://forums.macrumors.com/threads/whatsapp-not-working-9-1-beta.1913780/ Has anyone tried a clean install of 9.1 final and managed to activate Whatsapp?