Cannot Connect Home Sharing

I live in an apartment which has a wireless network. Both my Macbook and two AppleTVs are connected to the network. Both connect ok to the internet. The ATVs, however, do not see the MacBook telling me to turn on Home Sharing in iTunes. I have turned Home Sharing on and off many times and also tried my office Windows computer but without success. The set up works when I am home (I am working away) but not here. Is there anything that I can check with respect to the network setting?