I figured it out. (please mark this as the answer)
I don't understand why since I use a combination device of router/switch/firewall/wifi hotspot, but I had to enable the wifi card to get the display sharing to work, yet "cast to device" worked over wired.
I had disabled wifi in device manager because I never use it. Due to how my home network is set up, if the wifi is down so is the wired.
Also why does Win10 make it so you can't "run as administrator" for Device Manager from the Start menu search? I had to find a solution with a Bing search which told me to find the file in C:\Windows\system32 and right click from Explorer.
I don't normally log in as the admin, I long in as a limited standard user.
One final question.
The TV is in another room, and is much larger and has a much higher resolution than any of my monitors. Is there any way to do a mirror to either the primary or secondary monitor without making the TV a low resolution?
Such as having it scaled at 150% while the lower-resolution monitor it is mirrored on is 100%?
I suppose I can just start the stream, then move it to the Tv and hit <Windows key>-<Up arrow> to maximize it when I can't see anything.
Or should I mirror it at low res, get the display going, then disable mirroring so it goes back to maximum resolution?