If I have a 144hz monitor with a 1.4 port and also a 1.4 hdmi cable why does my screen go...

Make sure you're plugging it into the HDMI 2.0 port and not the HDMI 1.4 port, you may be in the wrong one.

And also, some monitors just don't support 1440p at 120-144hz, some only support it at 1080p 120-144hz. It's an HDMI and screen limitation.

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, and 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 info 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/

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/

It's nothing to do with your console...it is a limitation with your monitor.

Your monitor comes with 2 HDMI 1.4 ports (not 2.0)....120Hz and 144Hz are only supported via DP on this monitor, so this would be why it is defaulting back to 60Hz every time

Here's a forum thread on Linus Tech Tips about it (albeit with the better Series X but it's the same thing):

https://linustechtips.com/topic/1286444-monitor-cant-run-xbox-series-x-at-144hz/

Edit: Have edited the thread to provide more clarity regarding HDMI 1.4

The HDMI 1.4 cable only supports up to 144Hz at 1920x1080 resolution, perhaps this could be the problem. I recommend changing the monitor resolution to 120Hz or less.