I was having the same problem trying to wake from suspend.
If you are trying to wake from suspend then the ethernet may be going to sleep with suspend, check:
- that the tlp service is actually running.
systemctl status tlp
if it is inactive then enable it to make the service run permanently
sudo systemctl enable tlp
- Make sure that you have changed appropriate lines in the conf file at /etc/tlp.conf
Double check that you have removed hash to enable line, so it is not commented out.
TLP_ENABLE=1
WOL_DISABLE=N
This worked for me after taking quite a long time to work out what the problem is.
If you are trying to wake from deep sleep (shutdown), then the problem is different and I suspect it could be a BIOS setting.
Hope this helps a bit.