LG UltraFine 5K monitor - external devices not detected

I found a solution that worked for me!

Download the LG Screen Manager from their website under software, firmware & drivers: http://www.lg.com/us/support-product/lg-27MD5KA-B

Open the app and Install the latest software update while the monitor is connected. After it completes unplug all USB devices devices and the monitor, then plug them in again.

I contacted LG support, their response was:

I have discussed this with our technical team, the issue seems to be with the Mac not recognising the devices. We have raised this with Apple and they are looking into a resolution for this issue. We would advise to contact Apple directly also as they may be able to provide more information on this.

I contacted Apple support who had no idea about this issue. Their eventual recommendation was to reinstall macOS. This seems very over the top and I doubt it would work. I have reported it as a bug. If you have the issue I would suggest reporting as a bug and/or contacting Apple support to raise it up their list of priorities.

I opened a bug report with the Bug ID 35658244.

Please open a report with apple and reference this ID..the more people the more likely they fix.

open a bug report with apple and post the bug id for reference.

I don't know but its working fine still for me after the update... maybe reseting the monitor could do the trick. I also updated to macOS 10.13.2 around the same time.

This is still a problem in High Sierra. If anything it happens more regularly. There is no software update available in the screen manager, it says "(3.01,1.11,5234,3.00,0.1d) The software is currently up to date". The accepted solution does not work. Are you going to fix this Apple/LG?

Still a problem, of course. Basically after plugging the laptop into the USB-C connection to the monitor, I have to unplug/replug any other USB connections on the back of the LG for them to be recognized.

I also have this problem with the LG 27UD88-W (4k USB-C) monitor attached to my MBP-15 late 2016 TB.

My USB-A wired mouse is connected to the monitor directly and sometimes works, sometimes not. I rarely also have similar problems when connecting the mouse to a normal USB-C port via an adapter directly to the MacBook. I then have to change the port. This makes me thinking it is Apple, not LG, but in general, I know these USB issues are hard to debug.

The Monitor has the latest Firmware, my MacBook Pro is still on Sierra.

the latest firmware is 3.04,1.13,5237,3.04,0.1e

been running that since july..it was meant to fix a volume bug. nothing to do with usb.

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.

Why is this thread still marked solved?

This issue still exists.

also having this problem

firmware version?changelog?

you might want to wait a couple days/weeks..might be premature.

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.

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.