Q: External monitor no longer wakes from sleep (10.11.2 update)

The workaround fro resetting the displays I've been using is to set up the lower right hand corner as a hotkey that puts the display to sleep.  I just move the mouse as far to the right corner as I can, wait 20 seconds, then move it around a bit and most of the time it resets the displays without rebooting.  Sometimes I need to do it 2 or 3 times… it's a pain.  This seems to work to cycle the displays and get around this issue (mostly).

Thanks. Will try and hopefully verify your workaround.

I have been having a similat problem. After a number of reboots of my MacBook Pro (lid open) I opened the display preferences panel and set the resolution down to 1024 x 780 and then back up to the maximum.  My external monitor finally came back.  I haven't had the chance to retry this, so it could only be a random occuranc.

I have the same problem with a Mac mini 2011 2,7 Ghz Intel Core i7, 8 GB DDR3 RAM and AMD Radeon HD6630M 256MB. The Mac mini is connected to a Sony LCD TV via HDMI. It worked fine before the OS X 10.11.2 update. After the update, when the Mac mini is active, if i turn off the monitor or I switch the monitor HDMI input, after some time is impossibile to wake up the monitor without restarting the Mac mini. Before the OS X 10.11.2 update, pressing a keyboard key was enough to wake up the monitor. I have disabled all the energy saver options and tried the reset of SMC and NVRAM. The workaround of the corner that puts the display to sleep unfortunately doesn't work for me. Also I have tried Caffeine and Amphetamine apps to avoid the sleep of the monitor, but the situation is not changed. I have sent an OS X bug report to Apple.

I have the same problem.

Loosing connection between Mac Mini (Medio 2011) Running 10.11.2.

Connecting to a Phillips TV via standard HDMI cable.

When I reboot, the connection is back - but hardly a good solution.

Never a problem before - came with the 10.11.2 update.

Agree with most people in this thread - Apple has some serious problems with QA. What happened to 'It just works'...??

I also have a LG monitor connected through HDMI.  I am ****** off, I have a brand new 8 core Mac Pro, I just unpacked a few days ago.  El Capitan, and updated the OS the day I plugged it in (12-31-15).  My "energy saver" preference doesn't even have a "computer sleep" adjustment  slider at all.  Only Display sleep slider.

I am probably set up for phone assistance with Apple, I will try to call tonight and get help and post here if I get helpful response from them.

I had already set up a hot key for display sleep and that trick is not helping.  I am ****** I have to keep force shutdown'ing this computer the first week I have the **** thing.  Can't be good for it, and I can't leave it alone.

Here we go again.

Bernie

I want to sing this choir. I have a MacBook Pro (Retina, 15-inch, Mid 2015) which shows this exact behavior on an external ASUS 4k screen.

Support wants me to reinstall the OS, but judging from this thread, there's no reason to do so.

Guess I too have to wait for Apple to wake up and fix this problem!

If this is a secondary monitor, I would recommend trying what works for me in place of a full shutdown -- which is physically disconnecting/reconnecting the HDMI plug on the Mac.  I'll admit it's a bit sad that it has come to this point, but I do find jiggering the cable to be an easier and more painless solution than a full restart of the computer.  Maybe if I build a robotic arm to do this automatically, I can then sell it as an accessory in the Apple Store?

DId any developer manage to get his/her hand on the new beta (10.11.3 beta 2) to see if the issue was resolved?

The other workaround I've found is to use the hotkey to redetect monitors.

It's Cmd-F2 (although I need to use Cmd-Fn-F2 on my external keyboard.)

source: OS X: How to use multiple displays with your Mac in Mountain Lion and earlier - Apple Support

My method is to wake the computer up - I can see my laptop screen activate. My LG 29UM67 (Ultrawide) Displayport monitor flashes but doesn't really wake up. Then I press the key shortcut and it usually works after two or three goes.

It's not perfect, but it does mean I don't need to blindly reboot the machine or worse. Try it out

Thanks everyone for keeping the dialogue going.

Reminder -- Using MacMini 2011, connected to an Onkyo Receiver, which is connected to a Samsung LCD. This has worked for 6+ years across multiple different TV's, A/V setups, and 2x MacMini's until the latest SW update.

I've tried the hot corner method of putting the display to sleep, and then trying to reactive.  I've also tried the Fast User Switching/Sleep method which didn't work for me either.

Does anyone know how to downgrade back to 10.11.1 from 10.11.2?  I'm not sure if I have a TM backup of that but getting tired of waiting for a fix.

I will try the hot key method the next time I run into an issue

Hello, sorry for my English.

Same problem for me (Mac Mini mid2011 with Samsung FullHD) and I solved the problem this way:
before turning off the TV or monitor activate the monitor sleep function in one of the 4 corners. Then turn off the video. When it on again to get it out from sleep mode just click the tab or mouse.

For me it works.