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Question: MacBook won't detect external display

Hello,


A bit ago I purchased myself a MacBook Pro 15" (2016).

I purchased an adapter so I could connect it to my external monitor (which functions perfectly). It was a USB-C to DisplayPort adapter, after which I used a DisplayPort cable to connect it to my external UHD monitor (Philips Brilliance 288P).

The MacBook Pro was running Sierra as operating system, and it recognized the external monitor.


After I went through a bit of technical problems, however. Eventually, my 2016 model got replaced by a brand-new 2017 model. This one shipped with High Sierra, and is now running version 10.13.


Since the "update" to High Sierra (which I cannot revert, since it shipped with this OS X), my MacBook Pro 15" (2017) does not recognize my external monitor anymore using the exact same method I used before (USB-C to DisplayPort adapter).


The external monitor does not show up in the "display" section, and when connected and turned on simply goes to sleep. Normally it automatically detects a source and switches to that mode, but I also tried manually switching to DisplayPort as an input, after which I immediately receive the message of no signal being found.


I know for sure that the adapter works properly, as I have two of them which both worked before. Little tricks such as trying all USB-C ports, rebooting and reconnecting everything and booting in safe mode are to no use. Since using this new MacBook Pro with High Sierra on it, it simply acts as if my external monitor does not exist.


Does someone have any clue on what to do?

[Re-Titled by Host]

MacBook Pro with Retina display, macOS High Sierra (10.13)

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Nov 12, 2017 10:41 PM in response to xevtbng In response to xevtbng

The same thing happened to me this morning. My monitor was working fine as it's brand new. I installed High Sierra and it doesn't work anymore. I tried everything and called Apple. they couldn't get it to work. Now I find many people are experiencing this problem yet the Apple person didn't even mention it. I would like this to be a priority for them to fix asap as I need a second monitor for school. Sorry I'm in same boat:(

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Nov 21, 2017 10:53 AM in response to xevtbng In response to xevtbng

I had the same problem on an iMac 5k. Resetting NVRAM resolved it.


- - -


Shut down your Mac, then turn it on and immediately hold down these four keys together: Option, Command, P, and R. Keep holding the keys for about 20 seconds, during which your Mac might appear to restart.

- from How to reset NVRAM on your Mac - Apple Support

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Nov 20, 2017 11:44 AM in response to xevtbng In response to xevtbng

I just tried contacting support and they're still oblivious to this bug. I showed them the links to all the discussions including this one and they were still trying to make me check all my hardware and try resets. You know the stuff I thought of before wasting my time trying to talk to them.

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Oct 28, 2017 8:38 AM in response to xevtbng In response to xevtbng

you may have an out for this problem. I'm assuming you have one of the three mid 2017 15 inch models with touchbar. Even though they shipped with High Sierra as you say they were originally 'born' with Sierra 10.12.5. I would find an external drive to boot that has Sierra 10.12.6 installed and boot that 2017. If you are satisfied that all functions properly, I'm 99.9% positive it will boot and so you can then do a clean install and get back to running Sierra.


Many here will make you believe not true but I've been buying Macs for a very long time based upon this principle.

Oct 28, 2017 8:38 AM

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Oct 28, 2017 3:20 PM in response to Smokerz In response to Smokerz

I called my local Apple's technical support number, and I was told that I am not able to downgrade because it was shipped with it. So even if it is possible, if something happens and I screw things up, then I am at fault I suppose. I do not even have a clue on how to begin that process, nor would I prefer not to lose any data again (I do not have an additional external drive).


Does anybody know of another solution? Because it is not really a possibility to just keep using an old OS.


Has anyone who had the same problem for example gotten any success using a USB-C to HDMI adapter instead of a USB-C to DisplayPort adapter?


I did read somewhere that someone got it to work using Apple's USB-C Digital AV Multiport Adapter, however I am not sure whether I am willing to spend € 79 on an adapter to simply get my external monitor working with my MacBook Pro … while I have two adapters sitting there which used to work fine.

And then I still do not even know for sure whether it will actually work with my monitor …


Apple told me to try and sell my monitor and buy a new one. Philips told me it is up to Apple to decide what software updates they perform and they have nothing to do with that.

Both tell me that basically there is no way for me to tell which monitor would actually work with my MacBook Pro in case I would actually purchase a new one. Apple said that a newer 2017 monitor that is not dirt cheap is “supposed to work”. But even then, until which update will that one work?!

Oct 28, 2017 3:20 PM

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Nov 4, 2017 7:36 AM in response to xevtbng In response to xevtbng

It seems it's a recurrent problem High Sierra has when connecting additional monitors with an HDMI to... connection. I have the same with an HDMI to mini display plug on my iMac 27, similar when plugged in my MacBook Pro, but no problem when I connect it to my laptop via the HDMI port... We must probably wait until Apple decides to fix this bug...

Nov 4, 2017 7:36 AM

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Nov 12, 2017 10:41 PM in response to xevtbng In response to xevtbng

The same thing happened to me this morning. My monitor was working fine as it's brand new. I installed High Sierra and it doesn't work anymore. I tried everything and called Apple. they couldn't get it to work. Now I find many people are experiencing this problem yet the Apple person didn't even mention it. I would like this to be a priority for them to fix asap as I need a second monitor for school. Sorry I'm in same boat:(

Nov 12, 2017 10:41 PM

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Nov 13, 2017 6:54 PM in response to laurafromkirkland In response to laurafromkirkland

Sorry to hear that, it is so annoying! Like I said, when I called Apple support, I was told that any monitor from the second half of 2017 should work ... Apparently not.


I just keep hoping for an update soon as well, but the guy from Apple support told me that I needed to sell my monitor, as if there was not even going to be a solution.

Nov 13, 2017 6:54 PM

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Nov 20, 2017 11:44 AM in response to xevtbng In response to xevtbng

I just tried contacting support and they're still oblivious to this bug. I showed them the links to all the discussions including this one and they were still trying to make me check all my hardware and try resets. You know the stuff I thought of before wasting my time trying to talk to them.

Nov 20, 2017 11:44 AM

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Question marked as Helpful

Nov 21, 2017 10:53 AM in response to xevtbng In response to xevtbng

I had the same problem on an iMac 5k. Resetting NVRAM resolved it.


- - -


Shut down your Mac, then turn it on and immediately hold down these four keys together: Option, Command, P, and R. Keep holding the keys for about 20 seconds, during which your Mac might appear to restart.

- from How to reset NVRAM on your Mac - Apple Support

Nov 21, 2017 10:53 AM

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Nov 21, 2017 11:14 AM in response to fflanagan In response to fflanagan

I already tried doing both a NVRAM and SMC reset before, but I did it again just in case, and it made no difference.


If someone has a mid-2017 MacBook Pro and has gotten it to work on High Sierra, which exact adapter did you use?

Nov 21, 2017 11:14 AM

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Nov 21, 2017 11:23 AM in response to xevtbng In response to xevtbng

Someone posted this in another discussion last night and it's been working for people with iMacs and MacBook: http://www.displaylink.com/downloads/macos


Here's the post: Re: External monitor problem iMac 2017 High Sierra.


SMC reset did end up working for me though. I'm just running two monitors via adapters in the thunderbolt ports.

Nov 21, 2017 11:23 AM

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Nov 22, 2017 2:44 PM in response to alejandroveedub In response to alejandroveedub

Ahhhh had such high hopes ... installed the driver, but still no luck.


Should I try getting a USB-C to HDMI instead of USB-C to DisplayPort adapter? It is a gamble, but I really do not know what to do next. 😟


My screen is a UHD screen that can run op to 60Hz, I think, but HDMI support only seems to be at 30Hz now, and I cannot change it on the monitor manually or anything. So I am not even sure that anything will work at all.

Nov 22, 2017 2:44 PM

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Dec 2, 2017 1:54 AM in response to xevtbng In response to xevtbng

Well I had the same problem connecting a 2017 iMac to a secondary screen and have tried pretty much everything from fresh installs of High Sierra, VRAM etc... Downgrading to Sierra will solve your problem and I even thought about buying a USB-C monitor (until I saw the price!!) but eventually as a last resort I bought the Apple USB-C to Digital AV adaptor and this has solved by problems and things work now. Just one point though, I originally purchased a third party one, but did not work at all. In the UK the adaptor is £70 from Apple, but was able to pick it up for £45 from Amazon.

Dec 2, 2017 1:54 AM

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Dec 2, 2017 6:59 AM in response to Redchicken43 In response to Redchicken43

Do you mean now that you use the Apple USB-C to Digital AV adapter it works on Sierra or High Sierra as well?


I have searched some forums about this issue, and I think I mentioned here before that I have seen success stories about that particular adapter from Apple before in order to solve the issue.


Where I live, the adapter is € 79 (which is the £ 70 like you described). That is ridiculous. We do not have a local Amazon website where I live, though we are sometimes able to order through Amazon.uk, depending on the seller and conditions. Cheapest one I can find including shipping ends up being € 60. Which is less, but still ridiculous in my opinion.


Also, I am still not completely sure whether it will work or not on my monitor. It supports UDH HDMI monitors at 30Hz only, right? But I cannot set this manually on my monitor and it goes up to 60Hz. I do not want to purchase a € 60 adapter that will not even work. Ahhh, what a dilemma!

Dec 2, 2017 6:59 AM

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Question: MacBook won't detect external display