Co-op play: You do not have the required quest state to teleport to this player

I'm in New Game Act 1, trying to join a friend to help them clear Act 3. After joining their party, the game tells me:

"You do not have the required quest state to teleport to this player."

Has anyone experienced this before? I can't seem to figure a way out of this. Is this intended? Any help would be appreciated.

It seems like I now know more about the issue. For some reason, I cannot follow my friend in to The Black Chambers, even though I've cleared this area already. When he enters the area, the game does not allow me to teleport to where he is. Is this a bug?

I also have a "You do not have the required quest state" error.

I think that it's because the game allowed me to open the gate next to the grim tangle in the cemetery of eternals before I had the both items from the tombs (since I was playing coop). I have both items yet I cannot go further. I teleported on my friend to beat the boss in the cemetery.

I cannot enter the hunting grounds by waypoint nor by walking through the gate that opens when you beat the cemetery boss.

I'm under the impression that my game is broken.