Win10 updates, now can't go into hi-res display

My son's laptop was hooked up to a 4K 60hz display on HDMI 1. After an automatic update the laptop will only work with the monitor at a lower Hz on HDMI 2. For some reason, the computer isn't recognizing the monitor at 60hz on HDMI 1. If we hook anything else up to HDMI 1 on the monitor, it displays it. How can we fix this?

Edit: The monitor is an Asus MG28U. The computer IS going into 4K 60Hz, but the monitor is not showing up at that resolution/frequency on HDMI 1. If we use a lower resolution (another HD res Ultrabook), it DOES work on HDMI 1. It is sounding like a monitor problem

Hello @3DPiper,

3DPiper said:

After an automatic update the laptop will only work with the monitor at a lower Hz on HDMI 2. For some reason, the computer isn't recognizing the monitor at 60hz on HDMI 1. If we hook anything else up to HDMI 1 on the monitor, it displays it. How can we fix this?

[1] Do you know which Update it was?
[2] For a list of WU's . . .

> How to View Windows Update History in Windows 10

I hope this helps.