Apple TV can't "see" iMac for Home Sharing
I have my Apple TV and iMac on a home network and I use home sharing to view media from my iMac on my TV using the Apple TV.
My iMac hard disk crashed and I've had to completely rebuild - having done so, my Apple TV can't "see" my iMac - if I click on Computers on the Apple TV menu I get a message "To access your iTunes library on Apple TV, turn on Home Sharing in iTunes on your computer using <my Apple ID>".
Home sharing is turned on in iTunes.
From my iMac I can choose the Apple TV and play media on it.
Both machines are on the same local network (and same subnet - both with IP addresses 192.168.1.xxx served by the same DHCP server).
I've tried connecting both the iMac and the Apple TV to the network wired and wireless (I did this because I had this issue before my disk crash where the Apple TV could "see" the iMac if the iMac was connected to wirelessly, but not when it was connected wired - I never worked out why - now post the rebuild Apple TV can't "see" the iMac whichever way it is connected).
My Apple TV can access the internet - I can view media in the iTunes store.
My firewall (Little Snitch) has a rule to allow all incoming connections from local network - and it is not reporting any attempts to connect into the iMac that need a rule.
Any thoughts on what could be causing this?
iMac, OS X Mavericks (10.9), Aperture 3.4.5