Question for co-Op game in the Guild (Injustice 2)

Created the Guild, invited to her friend. Went to the multi universe, chose the mission, and invited a friend, he confirmed. We came together, it opened a window similar to king of the hill, and had to write a message waiting players. All further nothing happens, you can make full screen or exit. As then the two of us pass a multi universe?
Or is there a minimum number of players more?
For earlier, thanks for the reply.