When I change to 120hz it just reverts back 60hz

Hello, first it's a pleasure to be able to help you today.

My name is welcome to the community.

Hello Richardwilliams-789, I don't know what kind of monitor or TV it has, but it fails to recognize the capabilities of the console.

Usually the TV or monitor comes with these settings closed in the HDMI port, try to see in your instruction manual which is the high definition port and also how to access the settings.

I just tried to change it to 1440p 60hz, but it says this resolution isn't supported.

1080p is available to me in 120hz or in 60hz

4k is available to me in 120hz or in 60hz

But,1440p is only available in 120hz?

Are you sure it supports over hdmi?

Usually monitors support freesync 1440p 144hz with DVI or display port NOT hdmi

I believe that you need to have a monitor that is Freesync and Freesync has to be supported over HDMI, as well as, the monitor needs to have HDMI 2.0 ports and supports 120/144hz, looking at that Dell, being G-sync, it seems to have HDMI 1.4 ports which
limits it to 1440p at 60hz

A new monitor is needed if you want 1440p at 120hz,

Pulled this from a website...

Nowadays, most of the monitors, TVs, and graphics cards feature at least an HDMI 1.4 port which is enough for 144Hz at 1080p, 75Hz at 1440p, and 30Hz at 4K.

However, keep in mind that some monitors have limited bandwidth over HDMI 1.4 making it max out at 120Hz
or even at 60Hz in some cases (mostly G-SYNC and older monitors).

In fact, most 144Hz monitors are limited to 120Hz over HDMI 1.4, but some monitor manufacturers will use custom timing parameters, pixel rates, etc to use the full potential of the HDMI 1.4 bandwidth thus getting
144Hz at 1080p.

So, make sure that the exact monitor you’re looking at supports 144Hz or at least 120Hz over its HDMI 1.4 port –
or just look for a 144Hz display with HDMI 2.0.

HDMI 2.0 is also fairly standard and can be used for 240Hz at 1080p, 144Hz at 1440p, and 60Hz at 4K. The latest HDMI
2.1 adds native support for 120Hz at 4K UHD and 60Hz at 8K.

Here the link to the page..

https://www.displayninja.com/which-cable-do-i-need-for-144hz/

Hi,

It won't work sorry. The Dell Dell S2716DG doesn't do 120Hz over HDMI





I'm also pretty sure HDMI to display port is a dead end. A cheap HDMI to DP won't work, it has to be an 'Active' HDMI to DP, but also, I'm pretty sure the output device has to be DP capable (Xbox isn't) as well as
the input.

You're going to need a different monitor.

The best advice is to check reviews and look at the online manual's. Only if the manual says 120Hz over HDMI will it work at this refresh on an Xbox One.