Why is my Ethernet or Thunderbolt connection not working?

Mac-to-Mac Mode: Connect via Ethernet or Thunderbolt Only

Luna should connect automatically if it detects an active Ethernet or Thunderbolt connection between your Macs. You can also adjust Luna's settings so that Luna will only connect over an Ethernet or a Thunderbolt connection, instead of Wi-Fi.

In your Mac's top menu bar, click on Luna Display then Preferences. In the Mac-to-Mac tab, change "Allow any network interface" to your preferred connection method: Connect via Wi-Fi only, Connect via Ethernet only, or Connect via Thunderbolt only.

Troubleshooting the Ethernet Connection

On your primary Mac, open Network Preferences by going to System Preferences > Network, or by clicking on the Wi-Fi symbol in your Mac's top menu bar and selecting "Open Network Preferences". In the left side menu, select USB/LAN.

If your devices are connected via Ethernet, the Status will change to Connected and the left side menu panel will either say "Connected" or "Self-Assigned IP" under the USB/LAN option.

More Ethernet Connection Troubleshooting

make sure both ends of the Ethernet cable are fully connected to each Mac, or router or access point
restart your Macs, or restart your router or modem
create or switch to a new network location on your Mac

Here is Apple's support article for troubleshooting an Ethernet connection on a Mac.

Troubleshooting the Thunderbolt Connection

A Thunderbolt bridge needs to be established between your Macs before Luna can connect using a Thunderbolt connection.

Make sure you are using a Thunderbolt cable, as regular USB-C to USB-C cables (like the Mac's charging cable) will not work.

On your primary Mac, open Network Preferences by going to System Preferences > Network, or by clicking on the Wi-Fi symbol in your menu bar and selecting "Open Network Preferences". In the left side menu, select Thunderbolt Bridge and ensure that Configure IPv4 is set to "Using DHCP".

Once your primary Mac detects that it is connected to your secondary Mac, an IP Address will be shown in the IP Address section. The connection status on the left side menu panel will also change to a yellow dot and labelled as "Self-Assigned IP".

More Thunderbolt Connection Troubleshooting

make sure both ends of the Thunderbolt cable are fully connected to each Mac, or router or access point
restart your Macs, or restart your router or modem
check your cable to make sure it is Thunderbolt compatible

Here is Apple's support article for troubleshooting a Thunderbolt connection on a Mac.

While we do not recommend plugging the Luna hardware unit into any adapters or docks, using an adapter or dock for your Ethernet or Thunderbolt cable should not affect your connection through Luna.