It's fine and dandy loading into Cryo Archive in Marathon and looting it for all its worth—seriously, there's high-end loot everywhere—but you actually need to escape for it to count. The Cryo Archive extract system functions very differently from the other maps, where you casually stroll on over to an exfil beacon and beam outta there.
You'll no doubt find this out the hard way on your first run, when your backpack is full and you're looking to make an escape: 'wait, where are the exits?!' I'll explain the full process below.
