Changed by gamertag for the upcoming release of the MCC on PC, however when I go to check my stats now for Reach it says I haven’t played it before. However before I changed my gamertag I was able to view my stats, and can’t seem to find anything on it.
You’ll need to load Reach up on your new gamertag and play some campaign / forge / multiplayer / ect so that it can sync up with your new gamertag.