Both DisplayPort not working with Retina 5k, 27" iMac

Unable to get functionality out of either DisplayPort, using displayport cable direct from monitor to dock.

Monitor make is LG 27 UD69 - W (27") and running OS 10.15.7

Monitor works perfectly fine from displayport to thunderbolt (mac).


Thank you for contacting Plugable support! Sorry to hear about this issue. I’d be more than happy to assist you.

  1. Are other dock functions working as expected?

  2. Are you using DisplayPort to DisplayPort cables to connect your monitors? Or is there any kind of conversion happening between the dock DP port and the displays?

  3. Are you connecting the dock using the Thunderbolt 3 cable that the dock shipped with? Or are you using a third party cable?

Please don’t hesitate to let us know of other questions.

Thanks again for contacting Plugable support and best wishes!

Joshua Henry

Senior Engineer | Product Owner
Plugable Technologies

  1. Only charging capacity from other USB ports
  2. DisplayPort to DisplayPort Cables, no conversion.
  3. Switched to factory issued cable and this has fixed problem, though other issues persist detailed below.

I have tested as many ports as possible and they work, the bad news is the DisplayPort connections cause the monitor to flicker constantly and becomes unusable, i have noticed similar issues on forum and is there a way to fix this? I also reduced manually refresh rate on LG monitor with no luck

Thanks for the update, glad to hear there’s some progress from switching out to the stock cable.

For the flickering issue, in macOS Catalina and Big Sur there should be an option in the System Preferences --> Energy Saver called “Automatic graphics switching”, try disabling this and seeing if that may help:

We’ve been tracking some possible issues caused by this being enabled on MacBook Pro systems and I’m curious if it may also apply to the iMac as well.

Best wishes,

This option is not available on my iMac as I believe the dedicated graphics card is used always, as oppose to the laptop range. I have tried almost everything over last day including cable swaps and still persistent issue. What would be the best way to arrange credit/refund?

Thanks for the update and for checking that. I didn’t realize Apple had locked the iMac systems to only use their dedicated graphics, my apologies that it doesn’t appear the dock is going to work out for you.

If purchased from Amazon, you can request a refund there and they will provide you with return instructions. If you have any issues just let me know and I can reach out to you directly via email to further assist with the return.

Best wishes,

Thanks for your help thus far. Will arrange with amazon.

Kind Regards