Why is to doing this?

[Goku1814]

1st is computer 

2nd is xbox

Same HDMI Cord

[The_russian]

If you are talking about the different resolutions, the xbox one only supports the following resolutions: 480p, 720p, 1080i, 1080p, 1440p, and 4K. If the monitor has a native resolution of 1440x900, the highest supported resolution is 720p. The computer does support 1440x900, which is why it is able to display at that resolution. 

[Vishera]

The XBOX supports only 16:9 resolutions.

[Goku1814]

11 minutes ago, Vishera said:

The XBOX supports only 16:9 resolutions.

It was working earlier just fine at 1080p

[Goku1814]

14 minutes ago, The_russian said:

If you are talking about the different resolutions, the xbox one only supports the following resolutions: 480p, 720p, 1080i, 1080p, 1440p, and 4K. If the monitor has a native resolution of 1440x900, the highest supported resolution is 720p. The computer does support 1440x900, which is why it is able to display at that resolution. 

I'm able to select 1080p but the screen goes black and makes me go back to a lower resolution

[Vishera]

Just now, Goku1814 said:

It was working earlier just fine at 1080p

What is the make and model of your monitor?

[Goku1814]

Just now, Vishera said:

What is the make and model of your monitor?

Acer AL1916W

[The_russian]

1 minute ago, Goku1814 said:

I'm able to select 1080p but the screen goes black and makes me go back to a lower resolution

That's because you monitor has a native resolution of 1440x900, so it can't display 1080p.

[Goku1814]

Just now, The_russian said:

That's because you monitor has a native resolution of 1440x900, so it can't display 1080p.

It was earlier tho like 5 hours ago. Why isnt it now?

[Vishera]

Just now, Goku1814 said:

Acer AL1916W

Well,your monitor isn't capable of 1080p,because the height is less than 1080 pixels.

1 minute ago, Goku1814 said:

I'm able to select 1080p but the screen goes black and makes me go back to a lower resolution

Sounds like a bug,thanks to microsoft for leaving testing to the users 

[Goku1814]

Well can anyone help me figure out how to put the screen in 16x9?

[Vishera]

Just now, Goku1814 said:

Well can anyone help me figure out how to put the screen in 16x9?

The highest 16:9 resolution your monitor is capable of is 1280x720 or 1366×768,

If you want 1080p you will have to buy one.