Halo 5 nightfall armor is still locked

Hallo I’m sorry for my English

I got the halo nightfall from the halo mcc and watched it multiple times and still I don’t geht the armor I don’t know why I’m watching it on the Xbox one one the halo Chanel and I hope it is a big witch gehting fixed pls

Kann somebody help with their own experience pls a lot of thx dankeschön