Roku Ultra doesn't show up in network devices

Trying to "cast" my Windows 10 screen to the Roku Ultra, but it doesn't show up as a network device on 2 different Windows 10 machines.

They are all connected via the same router (Lan, not wifi).

All the other network items in our house show up, except the dang Roku.

Any ideas? Do they need to be on wifi for this to work?

 

Update- grabbed a wireless Windows 10 laptop, and I can see the Roku and screen mirror to it.

Must have to be on wifi?