New achievement wont unlock

I have infected 5 people in one round as the alpha zombie without dying in the living dead playlist and I did not get the achievement that requires me to infect 3 people in a single round. Am I doing something wrong?

Are you on an Anniversary map when it happens?

You need to do it on an anniversary map.

ok, thanks

Did someone quit causing blackscreen during the round? That tends to reset sprees.