Hi,
This is normal for the NEO, its a bit of a nightmare to determine if the device is actually “Active”. The green eth LED will flicker when there is activity. Beyond that, there is no indication of activity.
I just tried the DietPi image on a fresh installation, it seems to be working ok here.
The only thing I can suggest is connect up serial line, as per K-Plan’s suggestion if you have one. Its enabled by default.
If not, just try to verify the IP address in your router “connected DHCP clients” page, or similar. Maybe try pinging the IP also.
Failing that, if you are still getting issues, please let us know.