We had a bit of trouble at first getting some Acer K272HUL monitors to work with some Macs on campus, and Google searches came up with threads like this, which offered some helpful tips, but not a full solution.
So if you happen to have an Acer K272HUL (or perhaps a similar model) and some Mac desktops, you may find this post helpful.
Problem: We couldn’t get the Acer monitors to recognize our Mac computers (running Yosemite, though I’m not sure that made a difference) using HDMI cables. Then we tried using a MiniDisplayPort-to-DVI cable, and the Acer monitor recognized the connection but wouldn’t display at full resolution (we could get tiny resolution in the center of the screen or pixelated stretched resolution).
Solution: First, on the monitor, go to the settings and make sure the DP version is set to 1.1 and not 1.2.
Then get a MiniDisplayPort-to-DisplayPort connector.
That’s it. Full resolution.
Update (9 January, 2018): So the above blog post was for Mac Pros connecting to the monitor. If you try to connect a MacBook Air running High Sierra, the HDMI connection will “work” but may flicker. You should still use a Displayport connection.