Thanks Dukes!
@Kimsy: look at the North America column and note the channel numbers with a check mark. Those are the only 5 GHz WiFi channels that work on North American Roku players. The DFS channels are not supported. But also please let us know if you can see any wireless networks at all. I know in my home I can see over a dozen of my neighbor's SSIDs, and that's only the ones that have broadcast enabled. If you can't see any, I believe the TV is defective.
Rats, the chart didn't paste well at all. Just use any of the following channels for the 5GHz band: 36, 40, 44, 48, 149, 153, 157, 161, 165.
Dan
Roku Stick (3600), Ultra (4640), Premiere (3920), Insignia 720p Roku TV, Sharp 4K Roku TV, Nvidia Shield, Windows 10 Pro x64 running Serviio and Plex on a wired Gigabit network.