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Question: LG UltraFine 5K monitor - external devices not detected

Hi,


Few days ago I finally received my new LG UltraFine 5K display. I also purchased the new MacBook Pro (15 inch) with GPU upgrade, i7 upgrade and 1TB flash storage.


Connecting the LG display to the MacBook is working fine. However when I disconnect the LG display by unplugging the USB-C cable and subsequently reconnect the USB-C cable in the MacBook, the external devices in the other USB-C ports of the LG monitor are not detected.


I have a USB-C to USB adapter with a lightning cable for my iPhone plugged in & a Belkin USB-C to Ethernet adapter connected to my router. These two cables are not detected after unplugging and reconnecting the MacBook with the display.


I need to unplug both cables on the back of the display and plug them back in in order to have the monitor detect them.


Is this a known issue?

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Hi there JoelCraenhals,

It sounds like your USB-C devices which are connected to the LG monitor aren't detected when you unplug it and connect it again. I would suggest resetting the NVRAM and maybe even the SMC if that doesn't resolve the issue:

How to reset NVRAM on your Mac

Reset the System Management Controller (SMC) on your Mac​

Thank you for using Apple Support Communities, let us know how that goes!

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Dec 29, 2016 6:44 PM in response to JoelCraenhals In response to JoelCraenhals

Hi there JoelCraenhals,

It sounds like your USB-C devices which are connected to the LG monitor aren't detected when you unplug it and connect it again. I would suggest resetting the NVRAM and maybe even the SMC if that doesn't resolve the issue:

How to reset NVRAM on your Mac

Reset the System Management Controller (SMC) on your Mac​

Thank you for using Apple Support Communities, let us know how that goes!

Dec 29, 2016 6:44 PM

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Dec 29, 2016 7:00 PM in response to MoonJ. In response to MoonJ.

Thanks for replying.


What I did: I unplugged the LG monitor. Shut down the MacBook Pro and reset the NVRAM with Command+Option+P+R. When the MacBook Pro was completely rebooted, I plugged the monitor back in, but the devices (like iPhone and Belkin Ethernet adapter) where not detected. Unplugging the monitor one more time and connecting it again solved it and now the devices are detected, but had to unplug and reconnect the monitor. Is it a MacBook issue or more like a LG issue?


A question related to resetting the NVRAM: do I leave the monitor connected while shutting down and resetting the NVRAM?


Going to reset the SMC now on my Mac.

Dec 29, 2016 7:00 PM

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Dec 29, 2016 7:13 PM in response to JoelCraenhals In response to JoelCraenhals

The issue seems to be fixed without having reset the SMC. I just did an extra reboot and now when I unplug the LG monitor, the iPhone connected to the monitor still has power and when I reconnect the monitor all devices are detected on the MacBook Pro.

Issue resolved! Thanks a lot!

Dec 29, 2016 7:13 PM

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Jan 1, 2017 7:53 PM in response to sterling r In response to sterling r

Hi, I have this same issue repeatedly. I'm on a 13inch TouchBar MBP connected to an LG 5K Ultrafine display. I've done the SMC and NVRAM reset. Sometimes the USB devices attached to the monitor power up, sometimes they do it. It's proving rather frustrating given the cost of all of this kit. I never had issues with my old MacBook Air connected to an Apple LED Cinema Display.


Please advise. Seriously considering returning the whole lot at the moment as it's terribly buggy.

Jan 1, 2017 7:53 PM

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Jan 25, 2017 2:43 PM in response to JoelCraenhals In response to JoelCraenhals

I have the same problem with a Logitech USB dongle for the Mouse, Reboot, SMC, NVRAM will not consistently solve the problem, sometimes it works, sometimes it doesn't, I think this is a problem with the connection that once the MBP is plugged back using the supplied Thunderbolt 3 cable the monitor will not power the USB-C hub.

Jan 25, 2017 2:43 PM

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Jan 27, 2017 5:30 AM in response to JoelCraenhals In response to JoelCraenhals

I have the same issue.


When first connecting everything works.


When I need to disconnect my laptop, I eject any drives connected to the monitor.


Then when I reconnect the laptop, it's 50/50 on whether the drives connected to the monitor reattach.


This is incredibly frustrating, especially for such an expensive monitor.


I'm hoping their will be an update to address/fix this.

Jan 27, 2017 5:30 AM

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Feb 10, 2017 11:27 AM in response to JoelCraenhals In response to JoelCraenhals

Some have reported this issue and I've seen a version of this with my dual lg ultrafine 5k setup too. It seems to be that either the laptop or the monitors do not handle hot-swapping very well. I've seen that when unplugging the monitor from the laptop and then reconnecting, it doesn't consistently re-initiate the connection.


I've gotten around this by rebooting the laptop, but this is an annoying issue to be sure.

Feb 10, 2017 11:27 AM

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Mar 14, 2017 5:42 PM in response to JoelCraenhals In response to JoelCraenhals

I have the same issue. I am using 15" MBP TouchBar and LG UltraFine 5k monitor. My ethernet and usb connections out of the back of the monitor are not active when I reconnect my laptop. I have to restart with the laptop connected or unplug and reconnect the usb items to the back of the monitor.


Either solution is unacceptable and does not make me feel good about the thousands of dollars spent and weeks of waiting for this new set up.

Mar 14, 2017 5:42 PM

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Mar 16, 2017 9:08 AM in response to JoelCraenhals In response to JoelCraenhals

I am having this issue on my 13" non-touch bar. Monitor is awesome but the USB hub seems to not renegotiate when I disconnect and reconnect after a meeting. Extremely annoying. NVRAM and SMC reset doesn't do anything.

Mar 16, 2017 9:08 AM

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Question: LG UltraFine 5K monitor - external devices not detected