For those having trouble unlocking this, I had experienced the following:
I bought this a few months before buying a new Xbox console. I used the transfer cable / license transfer upon setting up my new system. I noticed that no achievements were unlocking for this and this would play in trial mode without being connected to internet. I had to select download again from the download history in account settings from the dashboard. It only took a few seconds to re-download so that this game would work offline. Once I did that, I replayed the first level and it unlocked. I also cleared the system cache just to be safe. I didn't delete my game save.
Make sure this unlocks first so you don't play through the harder achievements again.