When I enter a public game, I can only join Trailing the coven in act 1 and those before, though I've moved on with both my characters to lvl 35 in act 2? .. It noticeably strange and annoying .. Please help?

Had a wizard at level 35 as I overtook on quests with my witch doctor an since then I have been stuck in act 1 though I reached act 2 with my witchdocter and can play single player in act 2: S?