Halo 4 Legendary Campaign Problems

I finally got the time and the guts to beat Halo 4’s campaign on solo legendary. However, because I wasn’t signed into Live I don’t get the armor or the achievements??? Is this a common problem? The game’s been out for like 7 years now. What can yall do to fix this?
Thanks

Sadly the only way to get Mark VI Armor is to be signed into Xbox Live for this to work