I have a mid-2015 MacBook Pro running High Sierra. I normally use it as a desktop computer in clamshell mode with an external monitor.
I just replaced my 24-inch external monitor with a 32-inch monitor. The new monitor is an Acer EB321HQU-B, which is supposed to support up to 2560x1440 resolution.
According to the technical specifications my Mac is supposed to support
full native resolution on the built-in display and up to 3840 by 2160 pixels on up to two external displays, both at millions of colors.
Support for 3840-by-2160 resolution at 30Hz
I have the new monitor connected via a Mini DisplayPort to HDMI adapter.
But the best I can get is 1920x1080, which is the same as my old monitor. In Display preferences, the only options I see in Scaled are 1600x900, 1080p, 1080i, and 720p, whether I select 60Hz or 30Hz. So I can't show any more on the screen, it's just all scaled up 33%.
Is there some way I can take advantage of the new monitor?