Can't enable Home Sharing on Mac?

I had a problem where I couldn't seem to enable Home Sharing on my Mac.

In System Settings > General > Sharing > Media Sharing if you tried to turn it ON it would prompt for your AppleID and Password, then ask you to configure Home Sharing. Once you pressed DONE Media sharing would go off again.

I worked out a fix for this by doing the following:

Go to System Settings > Network > Firewall

Turn the Firewall OFF

Go to System Settings > Sharing > Media Sharing

Turn ON media sharing

You'll be prompted to enter your AppleID and Password, do so

Now enable Home Sharing - if successful you should see a dialogue "Hope Sharing is now Active"

Finally turn the firewall back ON, go to System Settings > Network > Firewall

Turn ON the firewall

Now you should be able to play your media from other devices on your network, e.g. play movies stored on your Mac from the Computers App on AppleTV