I think that when they launched season 7, they just removed the Elite Commander accolade in favor of costume store unlocks. The problem for us (who only were missing some optionals) is that we already had the gear. So store unlocking doesnt show up, the accolade doesn't register and, unless they fix that thing for us, we'll never be able to wear the type 3 costumes.
Same here, "Omega Force Shadow Operative" is the only accolade that didn't complete.
Its conditions are met, but it just doesn't register as done.
Frustrating. I did all this to finally get the "mk 12 Omega with optionals" look, and now I only can get the darn "MACO Style 3" look, which really is just MACO, not Omega.