I purchased more than one ticket but my reward status only changed once.
Your reward status increases with each movie showtime you see, not with each ticket you purchase. For example, if you buy 4 tickets for 1 movie showtime, your reward status will increase by 1. If you see the same movie on another occasion (a different date or showtime) your reward status will increase each time.
The Atom Rewards introductory offer of “See 4 movies, earn a free standard ticket” ended on December 31, 2018. Only members who saw their first qualifying movie on or before December 31, 2018 are eligible to earn a free movie ticket under the Atom Rewards offer.