Hi
I was told to post here regarding not receiving the helioskrill armour I have the legend achievement and spoke to an IAN regarding this he said he approves it and to post here and I will receive a response within 24 hours.
Please respond ASAP
Regards
Alex (Vyio)
I’m also having trouble, I have the achievement also
Go check through your armor in customization! I’m betting it’s in there because that’s where I found mine. It still hasn’t shown up in my collection
Hey I was having the same problem until I looked in my Spartan appearance and looked through all my unlocks of armour and it was in there for some reason it does not show in collection hope this helps 
It seems that the issue of unlocked armors (via the MCC) not showing up as unlocked REQ’s still persists. I hope this will be addressed at some point.
Take a look through all your armor pieces. Pay no attention to your collection because the helioskrill won’t show up as obtained. I believe you will find it mixed amongst your items!