I'm assuming this is a new Giga 4000 installation. If not please provide more background info.
My Giga 4000 is 2 weeks old. It is connected to my PC by an existing 20 ft ethernet cable with no issues. It doesn't matter which of the 4 LAN ports you use. You imply that your PC connects wirelessly is that correct? BTW when you connect an ethernet cable to your PC, its network card disconnects the wifi radio if there is a signal on the cable. So is there a signal on the cable? With your ethernet cable connected is the LAN port light lit on the Giga? Is your PC’s ethernet port light lit? If not, perhaps your cable is damaged, so try another one.
You don’t mention LAN port 4. What is on that port and is that port’s light lit?
With respect to trying to use the 10G port, that connection only works if your PC's motherboard has a 10G port.
I am puzzled by your comment around an unstable wifi broadcast as this is most unusual for the Giga 4000 unless it is quite far away. For example, my Giga 4000 is on the top floor at the back of a large 2 story house. A TV in the far corner of the basement is able to receive a 2.4GHz signal of 30-40 Mbps, and a 5GHz signal of 205 Mbps. I assume it’s too far away because you are trying to make an ethernet connection with your PC. But that may be an incorrect assumption. Cat 5/6 cable is limited to a max distance of 100m before needing a boost.
Also your PC can be data transfer intensive device. It should be connected to the Giga's 5GHz band if not using ethernet cable.
