There are a few armors in H5 that are unlocked by playing MCC:
- Mark VI GEN 1: unlocked by getting the “Your Journey Begins” achievement.
- Mark VI GEN 1 Scarred: unlocked by getting the “Cairo Station” achievement.
- Nightfall: unlocked by watching the Nightfall series included with new copies of MCC (must watch through Halo Channel app).
- Helioskrill: unlocked by getting the “Legend” achievement.
If you only played the first level of Halo CE in the MCC, then the only achievement you would have unlocked would be “Your Journey Begins”. If you are not seeing the Mark VI Gen 1 armor unlocked in Halo 5, then it likely means a sync error occurred between MCC and the Halo servers. The normal fix for this is to go back to MCC, change a customization option (such as multiplayer armor, emblem, nameplate, etc), save this change (it may help to play a round of multiplayer or something to ensure the sync happens), then check your REQ collection in Halo 5 for the armor. If you only played MCC through the free weekend and do not own MCC outright, it may not be possible for you to do this.
It’s worth noting that all the MCC armor sets can be gotten through REQ packs in Halo 5.