Hey,
Just a quick one to let you know that armour items that I unlocked through MCC and Nightfall (So, the Mark VI and Nightfall armour sets) are accessible to me during customisation, but still appear as locked when viewing them in the collection list.
You’re not alone, I’m experiencing the same issue.
Me too… It’s really annoying.
Likewise 
Come on 343, fix these issues!
Mine doesn’t show unlocked either but hopefully it will be fixed before I get too many others unlocked.
Got mine to show up just now. Went into MCC and was browsing the menu’s. Left the application open and opened Halo 5. Looked into my customization on Halo 5 and there they were. Hope this helps.
I am actually still waiting on my Teishin [Raikou] Helmet and Armor to be unlocked. The promotion says that I only need to play the game before November 7th, but it still hasn’t unlocked.