I do network support for a living.
Do you mind starting from the beginning again? Not sure if missing something. Seeing some info like "wifi works fine", but then "location does not have wifi". Also, "nothing between device and cable box", and use of term "patch cables".
If we can nail down some terminology (just to make sure we are both speaking same language and referring to same pieces of individual equipment).
Wifi works fine: I had the device at home, where I have wifi and set it up. Brought it to the site and connected it with known good network cables, and it would not connect. Did this with both modems.
Known good network cables: all the cables were connected to the single network jack on the modem, and to a computer. All the cables provided network connectivity between the computer and the modem.
Patch cables: Cables used to connect network items, going from switch to switch. Because you ask this later, all my crossover cables are bright red, so they can be *easily* identified.
1. What is your actual setup? Do you have a seperate cable modem and an additional router, or is this a cable modem with ethernet/LAN ports on the back (combination modem and router in single unit). Model number of the device(s) would be helpful. I am assuming you did not mean that you are trying to connect the Roku device to the back of a cable TV box. (if so, that connection will not work. Those ethernet ports are generally for diagnostics and not internet/network data transfer).
It is a cable modem, with no router, and it has one network jack on the back of it. It is provided by Spectrum. Person who owns this did not want to have wifi in his house. There is no cable TV box, only a modem. That's why he wants a Roku, to replace the cable TV, since he is paying $150 a month for TV. I have already had a conversation with Spectrum, and they state that their modem is working correctly, and I have zero evidence that there is a problem with the modem, other than the Roku.
2. Are the patch cables you are using just standard 5/6 straight ethernet cables? If so, since you have access to some network equipment, are you able to try using a "crossover cable" or at least a cross-over adapter on one end of the cable. (may be able to help isolate if there is an issue with your hardware. There is a possibility that there may be an issue with the MDIX function of your modem/router). Not high on the list, but still a possibility. As for your question regarding any known good brand cables, I have used cheap $ store ethernet cables to 20yr old hand-made ethernet cables I have lying around and they all work fine with the Roku devices. (RokuTV and Ultra).
addressed above.
3. Is it possible to take the Ultra to another location to test the ethernet capability? Or at least swap out the modem or router you are trying to connect it to. At a minimum, are you able to test the LAN port of the modem/router, as opposed to testing the cable? (since the cables already seem to be working with other devices). And you are sure you are plugging the ethernet cable into the LAN port and not the WAN port of your modem/router?
I have ONE network jack on the modem. it works with the computer. The cables work with the computer. The Roku is the only thing that I have plugged in to that, and not worked. For two Rokus.
Hawk