I have a 2009 macbook pro and a 2011 mac and cannot enable number sync on these devices. I still can make calls on them but uses my iPhone 6s plus to make the calls. They appear in the phone settings and they are enabled. I never received a message in FaceTime app if I wanted to use wifi to make calls. I was able to enable numbersync on my iPad 2. Just wondering if I'm missing something or what.