MacBook won't detect external display

Hello Apple,

I am facing the same issue.

We are runningg a media company where 3 screens are attached as external monitor to check output... They are a 3D cinema projector, Dell Monitor and Sony TV...

How can one buy all 3 monitors manufactured after late 2017? Just understand the issue and release the fix as we are currently broken down on our business...

Thanks,

Legato Labz

FWIW, I'm getting reasonable consistency with the following procedure, identical to many suggestions on this thread:

1. Restart MBP

2. Plug in dongle

3. Plug in HDMI

(my interpretation: Give the dongle drivers a few seconds to load, so HDMI will encounter a working interface)

Seems to be okay if I put MBP to sleep:

1. Put MBP to sleep.

2. Turn everything off

To re-start:

1. Turn everything back on

2. Bring MBP out of sleep.

Your mileage may vary!

March 14th when I went to bed, my Thunderbolt to HDMI worked fine with my external Samsung monitor. It's worked fine for the past 3 years.

Today, March 15th, I've spent all morning trying to figure out why it's stopped working. I've tried every suggestion in this thread. Nothing. Nada. I updated to Sierra 10.13.3 just a few days ago. My displays control screen doesn't show a "detect displays" button anymore either.

Could it be Mac is up to their old hijinks loading software updates as they do on iPhones blocking hardware from using third party accessories (in this case, a non Apple Thunderbolt/HDMI cable) from working if they are not manufactured by Apple?

I can't figure out any other solution however if I am rendered to go buy an Apple Thunderbolt/HDMI cable and it works, I am going to go ballistic.

I have a LG monitor with Thunderbolt 2 port. I had been using my new MacBook Pro (bought in Sept 2017) with the adapter of thunderbolt 3 to 2 and it was working great until the High Sierra update. I have called numerous times and even brought the monitor and laptop into the genius Bar. Sometimes it works and sometimes it doesn't. I did the update from yesterday and all of the sudden the monitor worked. The I went back to my work station today the monitor is no longer receiving a signal again!

I am at my wits end. It is an expensive monitor made for thunderbolt. I've tried all the resetting of the system, plugging in different ports, turining off and on.

LG blames apple and apple says it is LG's fault.

Has anyone else had the issue with the LG 34 thunderbolt monitor?

Thanks!

You must have your device set for automatic updates. today apple said there was an update for the apple store did i want to update, i said yes. They tricked me and did an update for high sierra at the same time and restarted my Macbook Pro. Since High Sierra if you do an system software update and it restarts your system one or more times it can cause issues with other device connect to your device. Apple is not aware of this or maybe they are. I advise everyone now, do not allow apple to do automatic updates and if you do any updates from apple, disconnect all devices from your system and after all updates are installed completely then hook all your external devices back to your computer. I think it's because the new security updates have to do with faults in the intel chips and power systems of the computer and during install restarts power surges thru your computer can nock out external devices, video adaptors and thunderbolt hubs seem to suffer the most.

Thank you, I tried this, as well as reinstalling the software and PRAM and nothing seems to work.

Is there a certain order in which these things need to be done. For example should the monitor be connected to the laptop before or after starting these steps?

I am using an adapter thunderbolt 3 (on macbook) to thunderbolt 2 (on back of monitor). I have tried all thunderbolt ports, different adapters, had all the cables and adapters checked for power.

This has been going on for 2 months. It will work for a week and then stop (happened 3 times), unfortunately it is stopped now and there seems to be no answers.

Could it be a driver issue with LG, like Apple tech says?

I can't afford a new monitor every time Apple does an update!

Thanks!

I have been running the external monitor with high sierra on my macbook pro 2017 for a few months now with no problem. Today, when the mac goes into energy saver mode, the external monitor does the same but does not awaken. ****
[Edited by Host]

I also have a similar issue with an iMac late 2015 running High Sierra. I purchased an ASUS VG248QE and connected it up with HDMI which worked well. But I have another device connected with HDMI so I purchased a Thunderbolt to DisplayPort cable and connected the Mac to the ASUS. Sadly it is not recognised no matter how many restarts or driver installs I perform.

I am having issues using my 2015 Dell monitor P2314H and my MacBook Pro 11/2015, it stopped working right after the HS 10.13.3 update at the end of February, does not recognize the monitor & goes into a power-saver mode.

I have wasted so much time on this issue, literally the last 3-weeks on this issue!! YIKES!! All to NO avail!

I have tried all the suggestions, tested ports at the Apple store & 2x with Apple techs phone, Dell - tested everything including the monitor ALL are working properly just not together.

I contacted both @DellCares and @AppleSupport for the same issue...

One of the tech guys suggested that perhaps the monitor needs a firmware update to be compatible with the latest version of macOS High Sierra 10.13.3?

Please FIX THIS Problem!! I need a monitor for my work and I am under a deadline, this is awful!!

I contacted both @DellCares and @AppleSupport for the same issue...

One of the tech guys suggested that perhaps the monitor needs a firmware update to be compatible with the latest version of macOS High Sierra 10.13.3?

All,

I have had the same issue with a Dell 2408 monitor, but recently my extended monitor is working on a regular basis. I used the following steps. All devices are off or disconnected.

1. Turn the laptop on

2. Turn on the external monitor

3. Connect the usb-c adapter to the Macbook Pro

4. Connect the HDMI cable to the usb-c adapter

5. Select preference on the MacBook Pro and go to Display

6. At this point, the screen on the MacBook may blink as it try to sink with the monitor.

7. Now you should see the additional display icon for the extended monitor. I changed from default to scaled with the resolution 1900x1200. Also, I attempted to reset the monitor to RGB.

8. Finally, on the main display icon I selected Generic RGB.

To date, I am maintaining a connection with both the extended monitor and my Macbook Pro even after the MacBook Pro goes into sleep mode and I wake it. So far so good now.

Is anyone else having this same problem?

Since the "update" to High Sierra 10.13.3 my MacBook Pro 15" (11/2015) does not recognize my external monitor using the exact same method I used before (USB to DisplayPort adapter).

I have purchased new cables, HDMI > < Displayport and Upstream > < USB -all to NO AVAIL

very frustrating, any ideas?

Apple techs... please fix this annoying issue...please

This trying to get my monitor to work with my MacBook Pro...

I tried everything suggested, I purchased new cables; HDMI >< Displayport and USB >< Upstream all to NO avail.

Do I need to get an adapter for the USB >< Thunderbolt 2?

Another lost week, looking for any suggestions or updates, this is so frustrating.

Yesterday I was on the phone with Apple support for 1 1/2 hours trying to figure out the best way to handle this issue, and it was suggested I get an adapter and try using the DVI port. DVI is the preferred port to use, newer technology than VGA.

I purchased the following to try on Monday:

1. Apple adapter HDMI > DVI $29.00

2. DVI < > DVI cable

3. HDMI < > DVI cable

I am determined to get this issue resolved and will submit an update tomorrow. I really hope & pray one of these does the trick.

Yep, external monitors/projectors are shotty since High Sierra. I have a couple year old 50" Sharp Aquos monitor that I can only mirror screens with from my MacBook Pro. If I try to use it as a second screen (like I've been doing in this class room since purchasing the monitor) it makes my MacBook Pro screen go dark. This is only since the High Sierra update. Ironically, my nearly six year old 26" Vizio still works fine at home as a second monitor. Interestingly, I have gotten the new Aquos to appear as a second monitor like twice since this problem began but only after resetting the PRAM and other start up procedures, but then no matter what I do the Display Preferences shortcut icon in the menu bar (for switching between second monitor and mirroring) doesn't appear anymore and I am forced to open system preferences to make any changes. Even when clicking "show in menu bar" nothing happens. And then the next time I come into the class room to connect to the Aquos I'm back to only mirroring. This is not external hardware issue because why would the old TV work fine and the new one not anymore. This is a software issue. Things were just fine before High Sierra.