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Mac OS Sierra external monitor issues

It seems that since the lastest upgrade (literally 2 days ago) I can no longer connect my iMac to my external monitor. The external monitor is now just blank and doesn't pick up any input. The iMac now no longer registers the external monitor so I am unable to select or detect the monitor.

I have even tried buying a new adapter thinking the cable/connector might have been playing up, but I still have the same issue.

Is this a known issue for Sierra and if so is there a solution to fix this issue?

About my Mac

MacOS Sierra 10.12.1

iMac (Retina 5K, 27-inch, Late 2015)

3.2 GHz Intel Core i5

8 GB 1867 MHz DDR3

AMD Radeon R9 M390 2048 MB

I have the same problem after macbook slept, reboot the system usually helped. But it's very annoying(

I have a similar issue on my Macbook Pro. The external display is not detected (no 'Arrangements' tab on display menu) although the internal display flickers off and on when external one is connected via thunderbolt. Using VGA and tried on TV PC input and OHP both with no success. Software up to date. Tried reset of NVRAM and SMC. This has happened since updating to MacOS Sierra.

MacBook Pro 15" Retina late 2013

2.3gHz Intel Core i7

16 GB 1600 MHz DDR3

NVIDIA GeForce GT 750M 2048 MB

Intel Iris Pro 1536 MB

There are apparently issues with Sierra and external monitors, being reported for a number of months now.

File a bug via bugreport.apple.com and hope, basically. :- /

Same problem here, macbook pro does not recognize external unless i reboot

Also happening for me - Late 2012 MBP, 10.12.1 - external monitor lost after sleep, or simply unplugging it and replugging it.  Just a black screen, but the laptop seems to detect it, as it changes the resolution.

I tried the SMC reset and PRAM reset - no luck

Any other ideas?  I have also filed a bug report with apple.

Hi fellows, instead of reboot try to choose "Sleep" in global menu first. It helped me.

Same think is happening to me, if the Max book pro goes to sleep with an external monitor as extended desktop then it doesn't show a picture on it although it knows it is there. I have an early 2013 13" retina pro with latest version of Sierra

Still experiencing this issue, for one brief moment I had my external monitor back up and working for a couple of days (no idea how I got the external monitor working again) until I reset my mac to update to latest Sierra update 10.12.2, thinking that Apple would have addressed this issue in the latest update. Now I am back to the external monitor being blank and no amount of resetting, sleeping and turning on and off my Mac works.

Did u get this working?

since upgrading my Mac Pro 2013 to macOS Sierra 10.12.4 I'm not able to use my 2nd external monitor, a Philips 27' monitor 273E3L using VGA to Apple mini port display connecter  it’s now displaying only a black screen but the power light is on! The 2nd monitor wont show up on the displays screen any longer!

Before the update today it was all working fine for 2 years and i plugged the monitor into my 2013 Macbook pro laptop and it works fine and it is running El Capitan 10.11.6so it has to be a Sierra problem! 

I got in touch with Apple Care on the phone and they took me thru reboots and various keyboard reboots and nothing! They cant rectify the problem and i contacted Philips who make the monitor and they said that  "As you say the screen is working on another mac with El Captain so this to me sounds like an OS specific problem following an update. I would advice you to contact Apple in that case.
Very frustrating now i don't have a 2nd monitor working!

UPDATE: So My Mac Pro hung last night so i thought sod it pulled out the power cord plugged it back in and bingo 2nd monitor and HDMI tv now all work????????? Go figure!

I am facing the same problem after upgrading to Sierra

I have a Macbook Pro Retina connected to an HP external monitor.

With Sierra I had no issues but after this 10.12.5 version I updated I started having problems.

When I connect the external monitor the Mac keeps on trying to detect the external monitor for minutes flashing from on off and changing resolutions.

Then sometime it detect it sometimes won't.

If I close the Mac monitor because I want to use the external monitor as for years I have done it shuts down the external monitor (I use in duplicate mode).

So this update is a mess for external monitor users because it adds detect problems, sleep mode problems and behaviors that I don't know if they will ever be able to repair and to get back as before. I'm afraid if they fix my macbook won't behave anymore the same way with the external monitor turning it off when I close the mac screen.

I tried the reboot opt cmd p r option but nothing works.

The Night Shift option says it should not work with external tv or projector, but if I activate it it changes colors of my monitor (so it works with external monitors LED or LCD but not TV and Pro).

Anyway I think thousand of Mac users that use an external monitor and update with this are going to have similar problems.

Hello to everybody, after many tries I solved the problem.

Macbook pro Retina detected the external monitor after many refresh taking around 1 minute.

That was really annoying! But now it is instantaneous!

The solution was on monitor settings and it's this:

Depending on your Monitor setting menu search for Monitor Input Auto Commuting and turn it off.

Leave the monitor on the input you are using i.e. HDMI 2 and the detection is in real time!

Before 10.12.5 the auto was working fine but now for some reason it's better to set the external monitor like that. In my case I don't use the external monitor as a TV or for other input so it's perfect not having the auto input activated. Anyway if you need it you can manually change the input from the monitor panel choosing the one you are going to use.

最後更新：2017-10-07 23:34:59

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