I was on a campaign with some people on my friends list. We were on Alien Oasis II and my game froze just as we killed Anubis, and when I tried to join/follow them, there was no join button on Plasma Pyramid. I know I bought AO2 pack but can't join Plasma Pyramid. I'm a level 34 archer, is the stage level limited? Or is Plasma Pyramid another pack I should buy?