I also get green light only lighting up for a couple of seconds on boot then yellow light flickering during usage as would be expected. I think, in that respect, your box is behaving normally.
When you say 'the dune is not seen on the net' do you mean no network access at all or just that other devices on the network cannot see the dune?
If it's the latter then SMB server needs to be enabled at Setup - Applications - SMB Server