ME3 Citadel - No message from Jack for Armac Arena

@MadPink42 I had this issue as well only with a Jack not romanced: you need to acquire her Arena license which I would suggest adding her to a battle, changing her gear in the next room and then leaving and going back to the apartment where you should get a notification from her wanting to use the Arena then, after the mission you should go back to the apartment and the option to invite her will pop off.