I had paralles 12 in my mac. But, the coherence mode had never worked since I install it. It grays out. I searched any possible solution in web and this forum. Does not work. First, do not tell me to 'Repair disk permission' for my Mac. Please notice that in Sierra, there is no such option in the dick window. ('Beginning with OS X El Capitan, system file permissions are automatically protected. It's no longer necessary to verify or repair permissions with Disk Utility.' from Apple. https://support.apple.com/en-us/HT201560 ). Second, I try to install it twice, which did not work. Also, please do not reply with something like 'please search some earlier post or some unclear solution, which really not make senses to customer. Thank you.