Net3 1 Port DMX Output not working

From your picture there, that is quite an old device - it's one of the first generation of 1-port gateways. I think you may need to use GCE to configure it, not Concert (I'll double check that later) - but to get it to that point you might need to update it. I would start by following these steps and using GCE:

https://support.etcconnect.com/ETC/Networking/Gateway_Configuration_Editor/Updating_1-Port_Gateways_to_be_Configured_in_GCE

Yes it is quite an old device, bought many years ago.

I can get to the bit to Update Software then choosing the 'Selected network interface IP address' option and when i click 'okay' the Net light and DMX light flash and go off for a second then they go back to normal (Net light on and DMX light flashing) but nothing happens in the GCE.

I tried clicking 'Switch to ACN' after the update and again the Net light and DMX light flash and go off for a second then they go back to normal again.

In order to update your device, you would need the DHCP and Update services running. If in GCE you go to the Network -> Configure Network and Services screen, you need it to look like this:

My guess is that maybe the update service isn't started - you can start it from that screen. Once that's running, give it another try.

I’ve started both of them but still just the same outcome

I’ve started both of them but still just the same outcome