External monitor no longer wakes from sleep (10.11.2 update)

15" MBP 2011; AMD Radeon HD 6770M;

Same symptoms. Sometimes starting system preferences/displays and fiddling-- most recently doing a 180° rotation-- will at least get the second monitor going again without necessitating a reboot, but something clearly amiss and seems to be software related. Started happening, as with OP, with 10.11.2 upgrade.

Energy PrefsPane in 10.11.2 El Capitan is different:

Am turning "Display Sleep" off to see if this will work as you suggest.

Flipping the monitor orientation (secondary) with SystemPrefs/Displays works. Then simply hit return to return the display to normal orientation (selects the default button "Revert" on the associated dialog box).

Same problem with a Mac Mini 2011 with El Capitan 10.11.2 connected via HDMI to Panasonic TC-L42E30 LCD Display, switched through Panasonic SU-HTB500 Soundbar. The soundbar manual says there is a 30 minute "inactivity" shutdown timer, after which time the display loses sync and cannot restore it. SImilarly to everyone else's complaints, the Mini's software driven display sleep is also incapable of waking. I have run the same setup for 5 years with NO issues, updated OSX last week, and now I have to power cycle the machine to wake the display.

Apple needs to fix this, multiple hard resets per day can't be good for my machine. It's certainly not good for my productivity.

Side note: wouldn't it be great if there was a keyboard shortcut that we could use to cycle display modes and resync video (*cough* fn + F4 in windows)? Constant poka yoke of removing useful features and critical failure analysis functionality is HUBRIS if OSX is not robust enough.

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