Can you verify that there is no firewall between the twp machines, including a software firewall? If there is make sure that ports 6101 and 10000 are open in both directions. Most times when we run into this issue is because the advertisement is not getting through.
If you want to verify the remote agent is running on the Mac server follow these steps.
1. open a command prompt on the media server
2. type in telnet macservername 10000
3. you should get a bunch of funny characters if the connection works.
You can do this test in both directions to make sure that both servers can communicate with each other.
Regards,