You need to install After Effects CC 2014.
You can install it from the Creative Cloud desktop application.
Please check these LINKs:
You don't HAVE to uninstall AE CC 2015. AE CC 2014 will install side-by-side with it. Although I must admit that for many people, keeping AE CC 2015 is like having a really neat but broken-down '63 Corvette Stingray in the garage with replacement parts on nine-month back-order. Or longer.
Cute answer Dave. At least I have proof that 2015 runs on my machine. Unlike 13.6
Thanks Kulpreet, much appreciated.