4k Not Working on Seiki Pro SM28UTR

Thank you for the quick reply. I am using the HDMI 2.0 designated port (HDMI 1) as identified in the user's manual. Additionally, I am able to get 4k to display using a different 4k source with this same HDMI port.

One other note, when I enable 4K support in Xbox settings it switches to 4K, but when I say "yes" to keep the settings it reverts back to 1080p @60Hz every time.

What kind of HDMI cable are you using to drive the 4K from the Xbox to your monitor? I believe HDMI cables rated as "High-Speed" are the ones that will support 4K. The cable included with the Xbox One S would definitely work (I'm using that cable on my 4K TV).
Also, what is the other "4K source" you can successfully get 4K on? Does that run at 60Hz? Does swapping the HDMI cables with your Xbox help?

Another thing, while the Xbox is connected to your monitor (even if only outputting at 1080p), navigate to your Xbox Settings. Go to...

Display & Sound > Video output > (Display) Advanced video settings > 4K TV details

What do you see? It's a checklist of various 4K features that you monitor may or may not support. You'll get a green checkmark, an orange "(i)", or a red "no symbol" on various items.

Thank you again for the reply, in response to your questions:

1. The cable I am using is the one supplied with the Xbox One S

2. The other 4K source is my GTX 950 GPU Card from my PC and yes it displays 3840x2160 @60Hz through the HDMI 2.0 port.

3. When going to "Display & Sound > Video output > (Display) Advanced video settings > 4K TV details" there are red "no symbols" next to everything except 4k @ 24Hz which is an orange i and 50Hz which is a yellow triangle.

I tried playing a 4k UHD blu-ray to see if it would display at 3840x2160 @ 24Hz, however the display only showed 1920x1080 @ 24Hz. I truly want to blame the monitor, but the fact that it works with my GTX 950 is what has me at a loss.

Hey there PianoIvy346074.

I've seen others have troubles using 4K monitors rather than televisions. Have you had a chance to make sure your monitor matches on the requirements on
this page? Also, be sure if your monitor has an auto-detection settings enabled, to disable them, as they can interfere.

The Xbox One S will run at 4K if the monitor does 4K@60Hz. When connected via HDMI, the HDMI port on the monitor must be at least version 2.0.

According to the product sheet, you should be able to get 4K@60Hz if you connect the Xbox to the HDMI 2.0 port on the monitor.

The other two HDMI ports, "HDMI 1.4" and "HDMI 1.4(MHL)" will not support 4K@60Hz, and the Xbox will likely default to 1080p.