Here is a session with a Steam invite.
Tl;dr: I figured out that the game actually joins the lobby, and I show up as in the lobby; however, the UI doesn’t pull up the game lobby.
First, I start a fresh session of Aoe2DE. Then I accept the invite to join my friend Anduin’s lobby. My in-game name is Ante.
Nothing happens with the UI for a minute (it stays on main menu). So I click Multiplayer, then Lobby browser. This is what I see:
My name, “Ante”, is the fifth player in this lobby. But my UI doesn’t show the game, just the lobby browser. My friend Anduin confirmed that I’m in the lobby. If I then try to click “join game” from the UI, then it gives this error:
After this, it kicks me out of the lobby, and Anduin confirms that I drop from the lobby. So I think the UI is simply not loading the game lobby. (In fact, the UI doesn’t do anything and just stays on the main menu. I had to click “Multiplayer > Lobby Browser” to find this.)
Here is the session log from this session:
This is also the same sequence of events if I accept an in-game invite and it hangs like this.