Achievement doesn't unlock

I keep doing the achievment to infect 3 players in match made infection but it never unlocks for me. Anybody know why?

It needs to be done on an Anniversary map, High Noon w/ Infection is in the Anniversary FFA playlist, so I advise trying there.

Wasn’t poppin’ and lockin’ a noble 1 or defiant map pack achievement? I got that one on an anniversary map, while crackin’ skulls with the oddball didn’t unlock when I did it on penance.

No, Poppin and Lockin achievement can be unlocked on any updated playlist. That was an Noble achievement. All of the DLC achievements unlocks very differently.