Can't pair Contour remote with new TCL Series 6 Roku TV

I just bought a new TCL Series 6 Roku TV and can't pair my Cox Contour remote to control it (power on/off, change inputs, etc.).

I'm able to control my TV's sound with the Contour remote, though, but that's because I have a Sony soundbar that's connected to the TV via optical cable, and I was able to find a Sony code that let me pair it with the Contour remote.  When I push the on/off button on my Contour remote, all that switches on/off is the Sony soundbar, and the TCL TV doesn't change state.

I've tried all of the TCL-specific codes that Contour remote setup suggested, but none of them work, so for now I'm stuck having to use both the Contour remote and the TCL remote.

Has anyone else encountered this issue where you can't pair the Contour remote with a TCL TV? If so, how did you fix it?

Thanks in advance!