It is not often that we find Microsoft apologizing for an issue with one of their flagship games, it comes as a supirse when Microsoft announced that a place holder file may be all people who downloaded Halo 5 guardiands got this week. If you use the instant on feature, and pre-ordered you may have ended up getting burned on this one. Though Microsoft says  only a “small number of players” are effected.

People who downloaded this stub file will need to delete it and reinstall the right one. You can check to see if you installed the stub file by following the instructions below:

1. Go to My games & apps
2. Sort your game collection by selecting Installed à Sort by size
3. If your Halo 5: Guardians game size is greater than 40 GB, you’ve got the correct version
4. If your Halo 5: Guardians game size is less than 40 GB, you’ve got an incorrect stub file.

if you got the incorrect file you will need to re-install.

story via Halo waypoint