Well, the One S upscales to 1080p to 4K as sadly it’s not as standard.
First, try a compete console restart, I know it sounds obvious, but a console restart from settings may solve it.
I’d check your have got your TV in game mode. Check the TV can accept 60Hz. Maybe a health check on your console and have a clear out of anything on the hard drive that could slow it down ( old game installs, save files, music, vids etc )
Again, remember to restart console after deleting anything from HDD so it takes effect. More housekeeping than anything but good to stay on top of your console.
Clear your Cache ( old skool but works )
I’m pretty sure the XOS comes with 2.0 HDMI, but make sure you’ve got one sorted just in case it’s gone walkies.
Failing that, look into a Project Scorpio next time you upgrade console, or even a Scarlett. Bare in mind that it’s Xbox One Enhanced now so it’s visually stunning