Resolution only 640x480 on 1920x1200 monitor

[PateON]

I installed new Windows 10 x64 on this computer (HP EliteDesk 705 35W G4) with a 1920x1200 monitor. DP cable. During installation, the resolution was only 800x600, and after installing the graphics card drivers it was only 640x480 without the ability to change anywhere. On the FullHD 1920x1080 monitor everything is fine (DP cable to DVI, DP cable too), but on the necessary 1920x1200 monitor the resolution is only 640x480. Why? I also added the drivers from the monitor manufacturer to the system, but it did not help.

[DGroves]

first of all video monitors do not require a driver as the devices video resolutions are hard coded 

second not every monitor is able to display every resolution

third this model  EliteDesk 705 G4 comes in various configurations mini desktop, small form factor and minitower

so without the monitor model number and a correct system model, not much that can be done as i have no way to start troubbleshooting as some system have only onboard video and some have a optional add in video card

https://h20195.www2.hp.com/v2/getpdf.aspx/c06040429.pdf