you need to plug your series x into hdmi 4. on series x, go to tv settings and change refresh rate to 120hz. it's not automatic, you have to initially change it manually
why is 120hz hyper important? you know that literally only a very few selected games do 120 and that's usually dynamic resolution. 120hz is a pipe dream currently. anyways, just unplug everything from Xbox and tv (including hdmi cables), wait a minute, plug hdmis first then power cable. once you do that, go check again. also make sure to have input signal plus is selected on hdmi 4 (well, all hdmis really). also turn on cec just in case as well.
