Why is some of the Halo MCC armor still locked

Games Halo 5: Guardians
1

i completed all of the campaigns in MCC on legendary a while ago and still don’t have the armor you get from doing this

2

Which one specifically are you talking about? Helioskrill? Mark VI Gen 1 (normal or scarred)?

3

helioskrill

4

There are countless threads in here with the answers to this.