I am trying to get my second hololens to join the shared session in holo academy 240 chapter 3, but it isn't joining. I am able to place the anchor just fine when the first hololens joins the session.
Solved! The 240 tutorial seems to skip over this step but I fixed it by launching the Holotoolkit sharing tab found at the very top of the Unity editor. (next to Component and Window)
After launching that it gives you the computer IP address in a console window. Then you build your project without exiting the console window. In visual studio you build without debugging and it creates the session using the console window.