Help from halo reach bug!

I have problem on halo reach :joy::sob::sob::sob::sob::sob::cry::cry::cry::cry::cry::cry::cry::cry:
Me and my friend we did less 3 hours in légendary and we don’t have the achievement :cry::cry::cry::cry::cry::cry:
Look the Stat from XzExterminatioN and Demoxicini

According to your Halo Waypoint profile, you haven’t completed the final three missions.