This achievement is now obtainable and should unlock retroactively once you install the newly released update (version 2.2.12142.0).
Dec 16, 2015:
"Whooooaaaaaa! Hey, everyone! I know it's been a hard couple of months, but I've got word that there's an update released today that should fix everyone's achievement issues (as well as some other issues with performance, network, and purchases). The even better news is that it should be retroactive, and you should NOT have to earn your achievements again!
Please make sure you update. You may not see the update available until tomorrow, though, but keep checking the Store for the update and let us know how it goes. :) Thanks again to everyone's patience! For now, I'm going to verify this post so that everyone can see that an update has been pushed without digging for this post on page 5. If there are any other issues noted, I'll remove it so that no one thinks this is resolved. :3"