@jmone Thanks for pointing me in the right direction!
After more research, I had to enable 4k content by individual HDMI ports on my receiver. Not sure why Sony made that a manual option.
That got Netflix 4k working straight away through my TiVo.
It took more research to figure out I had to download Microsoft's HEVC Video Extensions (for $0.99) to get Netflix 4k to work on the PC.
After doing even more research it doesn't seem possible to stream 4k content on a Windows PC for Prime Video, Disney Plus, or Hulu either through their respective apps or through a browser. Is that your understanding as well?
My next question is regarding playing HDR on the PC:
In Windows Settings --> Display --> Windows HD Color settings --> Display Capabilities
Stream HDR Video = No
Use HDR = No
Use WCG Apps = No
I assume that means videos won't play in HDR? Can I get video to play in HDR?