Did you figure it out? I'm stuck on that part and the part where you have to punish Leah after a service check in the lobby.
I used all day to get the solution finally, you have to download the 0.60.2, you will see the spanking bench, and then solving the mission about Nadia will unlock the serve in the lobby. I think that is a serious bug. Therefore, there is no guarantee that the same event will not occur in the following content.