Since I upgraded my iPhone and iPad to iOS8, iMessage on my Mac no longer syncs with the iCloud account used on those devices. I checked the account under "internet accounts" and there is now no longer an iMessage option to tick, and so it doesn't appear under "accounts" in iMessage. That obviously explains why its not syncing with my iphone/ipad but not sure what to do to fix it. I've tried deleting the account of the Mac and entering it again, but same result. The only possible problem I've noted is my account is an @me.com account. On my iPhone/iPad I now see both a @me and @icloud account with the same name listed (and ticked) under iMessage/FAcetime. But under the iCloud account settings its the @me.com account thats signed in. I tried adding the @icloud account as well on my Mac, but it just said its already signed in and took me to the @me account of the same name.