External display not recognized after waking from sleep until restarted

Solution 1:

I still have the same issue on a macbook pro 15' 2018.

Unplugging and plugging again the screens helps without having to restart the whole thing... except that all open windows jump to the main screen.

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///// EDIT solved the issue through an external thunderbolt dock

I am using the Thunderbolt 3 Dock of Glyph now. My external screen is connected to its Display Port port. After waking up the screens behave normally. When I take a break, I power off the external screen and power it on before waking up the computer. In the tips I got from Glyph, they do ask you to turn off Energy Saving options when connected to the dock, but it all seem to work fine,

Solution 2:

I've found the system knows the other monitor is there, it just can't rouse it. Fastest work-around I've devised so far:

1. Open System Preferences
2. Go to 'Displays'
3. Click 'Gather Windows'
4. On the panel for the external display, choose one of the rotation options. (Seems that forces the system to give itself a kick and the external display will wake up, albeit upside down.)
5. Helpfully, there's a 'Revert' button already focussed. Just press Enter on your keyboard and it'll spin back around.

Done.

Solution 3:

I experience similar problem and Google brought me here. Though as long as I don't unplug the cable it would always work fine. If I unplug it to take away the laptop and come back again one of my two monitors (the one converted from Thunderbolt to HDMI) won't work. However the other one with Thunderbolt to DisplayPort always works.

My solution is to connect it to a different port and most of time it would just work again.