Just finished building a new PC and it's connected to my Google network over ethernet and internet etc all fine, but the device will not show up in my device list in the home app, which means I can't reserve an IP and setup port forwarding etc.
When I download something on the PC, that real time use is picked up in the app, but not the device?
It sounds like the PC is not configured to use DHCP to get an IP address assigned dynamically. Take a look at those settings first. Once you switch it to DHCP / dynamic, it should show up in the list in the Google Home app.
That's certainly puzzling. If it's connected through the LAN port on the Google WiFi, and it's using DHCP, and you can see the usage in the app, it really should show up in the list. I can't think of any reason it wouldn't.
Just one quick final check in here since activity has slowed down. We'll be locking the thread in the next 24 hours, but if you still need help, I would be happy to keep it open. If there's more we can do, just let me know.