Heyo. So I’m a huge Halo Achievement Hunter, if we can say that in 2019. But I having trouble with the Monopolized Achievement. After months of suffering I did manage to make it under 3 hours but it didnt gave me the Achievement. Please I dont want to suffer anymore, GIVE… ME… THAT… CHI… Achi. 
My current time is: 02:58:17 (dont laught)
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> Heyo. So I’m a huge Halo Achievement Hunter, if we can say that in 2019. But I having trouble with the Monopolized Achievement. After months of suffering I did manage to make it under 3 hours but it didnt gave me the Achievement. Please I dont want to suffer anymore, GIVE… ME… THAT… CHI… Achi. My current time is: 02:58:17 (dont laught)
Any skulls on that would get rid of your multiplier?
Nope.
Didn’t activate any 0:00x multiplier skulls.
Only Pinata was active. It’s a 1:00x.
I read on another thread (don’t have the link, sorry) that they are aware and working on a fix because there have been a number of posts similar to yours. So don’t fret 
You should be okay as long as they times are recorded on your service record on Waypoint.
Hey OP, the best place to report issues like this is in the achievements thread that is pinned at the top of the main MCC forums. This issue in particular is known to 343 and they are actively investigating it now