Hello @George_Finch
If Roon Server runs on a Mac and your endpoints disappeared after updating to macOS 27, this is why, and here is what to do while we work on it.
macOS 27 blocks Roon Server from making outgoing connections to other devices on your network. The block happens inside the system’s network stack, before anything leaves the Mac, so Roon reports it as “No route to host”. Incoming connections are unaffected, which is why Roon itself still runs and your remotes still connect while your speakers and streamers vanish.
Toggling the Local Network permission does not clear this, and neither does reinstalling Roon. That is not you doing something wrong. There is currently no way to reset this state on macOS at all, which Apple have acknowledged.
Step 1: find your network address
Open Terminal. You will find it in Applications > Utilities, or press Command and Space and type Terminal.
Paste this and press Return. It only reads, it changes nothing:
ifconfig | grep "inet " | grep -v 127.0.0.1
You will see one or more lines like this:
inet 192.168.1.42 netmask 0xffffff00 broadcast 192.168.1.255
Take the address after inet, replace the last number with 0, and add /24. So 192.168.1.42 becomes 192.168.1.0/24. If yours reads 10.0.0.37, it becomes 10.0.0.0/24.
If your line shows a netmask other than 0xffffff00, please post the output here instead and we will give you the right value. That is uncommon on a home network.
Step 2: apply it
Paste both blocks below into Terminal, one at a time, pressing Return after each. Replace 192.168.1.0/24 with your own value from step 1, and leave 224.0.0.0/4 exactly as it is. Terminal will ask for your Mac password. Nothing appears as you type it, which is normal.
sudo defaults write com.apple.network.local-network AllowedEthernetLocalNetworkAddresses -array "192.168.1.0/24" "224.0.0.0/4"
sudo defaults write com.apple.network.local-network AllowedWiFiLocalNetworkAddresses -array "192.168.1.0/24" "224.0.0.0/4"
Run both even if you only use Wi-Fi, or only Ethernet. They are separate settings and the unused one does no harm.
The 224.0.0.0/4 entry is not optional if you use Roon ARC. macOS treats multicast as local network traffic whatever else you exempt, and without it ARC cannot set up its connection.
Step 3: restart the Mac
Nothing changes until you do. After the restart, open Roon and go to Settings > Audio. Your devices should be listed again.
To check it applied
defaults read com.apple.network.local-network
No password needed, changes nothing. You should see both lists with your network and 224.0.0.0/4 in them.
What this trades, and how to undo it
This tells macOS to stop treating your network as a local network for every app on that Mac, not only Roon. It is the mechanism Apple provides for exactly this situation, but it is broader than Roon, and worth knowing before you run it.
To remove it later:
sudo defaults delete com.apple.network.local-network AllowedEthernetLocalNetworkAddresses
sudo defaults delete com.apple.network.local-network AllowedWiFiLocalNetworkAddresses
Then restart the Mac again.
This is a workaround, not a fix. R&D is working on the underlying cause. We do not have a timeframe.
