Did you use the same Apple ID and password when setting up home Sharing on both machines.
From another thread
For anyone else reading this - I just went in to the advanced menu and turned off home sharing. Then I went back in and turned it back on - I chose the user/pass of another one of my computers, then clicked into that library - and the buttons I needed were immediately there.
In itunes 11 the Menu is
File > Home Sharing > Create home share
Suggest you turn off home share on both machines and recreat the home share using the same Apple ID and password on both machines