I have a brand new MacBook Pro (2018) with two external monitors (AOC Q2790PQU), connected via a Kensington SD5200T docking station (1 x HDMI and 1 x DisplayPort).

The Mac is closed when connected to the docking station.

Whenever I lock my screens, after seeing the login screen for some seconds, both external monitors turn off (go black). I would like the monitors to remain on, showing the login screen.

Does there exist a setting for this somewhere?

Also, for some reason, when I press some keys on my keyboard or move the mouse to wake up the monitors (the Mac itself is not sleeping), then only one of the monitors will turn back on.

In order to get the other monitor to turn back on, I need to open the Mac lid, disconnect and reconnect the docking station, and then close the lid of the Mac.

Does anyone have any ideas why this is happening and how to fix it?

  • what is the behavior if you don't close the lid of the MBP?
    – dwightk
    Commented Feb 8, 2019 at 14:01
  • 1
    If I open the lid of the MBP, then all three monitors will remain on at the same time. Due to lack of desk space and too low height on the external monitors, I need to close the lid of the MBP.
    – leifericf
    Commented Feb 8, 2019 at 14:02

2 Answers 2


As this answer from @leetbacoon states,

Open Terminal and run the following:

caffeinate &

This will keep your display on until caffeinate is killed (you can quit Terminal if you want).

To disable caffeinate, run this in Terminal:

killall caffeinate

I've just tried it too and it worked for me (MacOS Monterey).


I finally managed to pinpoint the issue: Display Port cable.

One of the monitors were connected with a Display Port to DisplayPort cable. After switching from a Display Port to Mini DisplayPort cable, everything seems to work properly.

One monitor is connected via HDMI (from dock) -> HDMI (monitor 1 input); the other via DisplayPort (from docking station) -> Mini DisplayPort (monitor 2 input).

This also meant that I had to change monitors, because the aforementioned AOC monitors did not have a Mini DisplayPort. I'm now using 2 x Lenovo ThinkVision monitors (model: P27q-10).

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