13" MacBook Pro 2020, two external monitors flicker together


We’re using a Plugable UD-6950Z with a MacBook Pro (13" 2020, four Thunderbolt 3 ports with Big Sur). Our goal is to have the laptop closed when connected, and to use two external Dell P2217H monitors with it.

We downloaded and installed the DisplayLink Manager Graphics Connectivity application and are able to get the two external displays working with the laptop open, but when we close the laptop the screens flicker and the laptop’s display is still showing active as if the laptop were open.

We’ve tried this with both DisplayPort connection and HDMI, but neither seems to work. We’ve restarted the computer several times and made sure to allow its requested access.

Please let us know if there is any more information we can provide!

Thank you!

Hi Pat,

Thank you for posting, and for the excellent detail you provided that is much appreciated.

Using a Mac laptop with the lid closed is known as clamshell mode or closed-display mode.

Your description ‘MacBook Pro (13" 2020, four Thunderbolt 3 ports)’ suggests that you are using an Apple MacBook Pro that has an Intel processor (CPU). Please correct me if I am mistaken.

Presuming for the moment that my understanding is indeed correct, in order to use an Intel-based Mac laptop with the UD-6950Z docking station in clamshell mode, the Mac must be running macOS 12 Monterey and an external power source must be connected to the Mac (the UD-6950Z does not product power to the laptop).

We speak to this requirement in our knowledge base article here → https://kb.plugable.com/questions/724337

It unfortunately is not possible to use an Intel-based Mac in clamshell mode in conjunction with the dock when the Mac is running macOS 11 Big Sur (as you mention you are), which is why clamshell mode is not working.

That said, we have had reports that others have used the free ‘Amphetamine’ application → https://apps.apple.com/us/app/amphetamine/id937984704?mt=12 on their Intel-based Macs running macOS 11 Big Sur as a workaround.

To expand further, the Amphetamine application can be used to prevent the Mac from going to sleep when the laptop lid is closed. This action can supposedly help circumvent the behavior you are presently experiencing.

** Please be aware that we have not tested this workaround nor could we provide support for the application’s use. We make mention of the potential alternative others have reported only as courtesy **

Thank you,

Plugable Technologies

This topic was automatically closed 20 days after the last reply. New replies are no longer allowed.