Plugable USB-C Triple 4K Monitor Docking Station not connecting to 3rd screen

USB Docking Stations UD-ULTC4K
1

Hello
All was working well until this morning.

I have 3 screens:
1 4K screen connected with HDMI
1 4K connected with display port
1 4K connected with HDMI

MacOs Venture 13.6

I can only connect 2, it doesn’t matter whether one is HDMI and Display Port or two are HDMI.
I have disconnected everything. Restarted. Added cables one by one and each time the same result, only 2 will connect at one time.

Please advise how to fix this. I have read through your forums and cannot fix.

Thank you.

2

Hi Mel,

Thanks for reaching out to Plugable support! I’d be happy to help with that.

To investigate this further, it would be very helpful if you could let us know which ones of the display connections are functioning in which ones are not. specifically on the back of the docking station, these display connections should be labeled as display 1, 2, and 3.

This information is important as it helps us to figure out which portion of the display technology contained within the stocking station seems to be presenting an issue for your connection.

It did also want to confirm if you are using the USB-C cable that came with the original docking station to connect it with your computer.

Thank you for giving us a chance to help.

Richard A
Plugable Technologies
https://plugable.com/support

3

Hi Richard

Thank you for your response.

All display connections work. Its that only 2 will work at one time whether it’s hdmi or display port, it doesnt matter.

Yes im using the usb cable that came with the the docking station.

Mel

4

Hi Mel,

Thanks for the update.

I did want to ask if there was any pattern to the two displays that are working versus the 1 that is not. For example, is the one using display port connection not working versus the two HDMI connections are working.

Are you able to get displays connected to display 2 and 3 on the back of the docking station to work, but not able to get a display connected to the display 1 to work?

Any type of patterns to how these are able to successfully connect would be very helpful in narrowing down what could be happening.

One important thing to note when it comes to this type of docking station is that there is a large difference between the display 1 connection and the display 2 and 3 connections labeled on the back. This particular docking station utilizes two very different types of display technologies in order to connect displays. So it is important to make the distinction if one is working and the others are not.

Thank you for giving us a chance to help.

Richard A
Plugable Technologies
https://plugable.com/support

5

Hi Richard

Thanks again for your response.

Display 2 and 3 work with HDMI. If I add an HDMI or DP+ to Display 1, Display doesn’t work.

Display 2 and 3 work with HDMI and DP+. I add HDMI to Display 1, Display 1 still doesn’t work.

So I’m guessing you’re right, it’s the issue with Display 1 but with both HDMI and DP+.

Mel

6

Hi Mel,

Thanks for the update.

This information is very helpful as it indicates that there is an issue with the Alt Mode connection to the docking station.

For the display one connection to work, it does require that the host computer has a USB-C port that supports DisplayPort Alt Mode for extending displays. Based on your description, we know that you are using a MacOS device and that should support extending displays through the USB-C Thunderbolt ports.

The next thing that we want to verify is that you’re using the USB-C cable that came with the original docking station to connect it with your computer. The reason this is important is we need to make sure that you’re using a USB-C cable that also supports DisplayPort Alt Mode functionality as not all USB-C cables do.

Hopefully, knowing these requirements will help to understand why that port is not working.

Richard A
Plugable Technologies
https://plugable.com/support

7

Hi Richard
Thanks again for your response.
As I mentioned above, I am using the USB-C cable that came with the device.
I have Three Thunderbolt 4 (USB-C) ports.
Mel

8

Hi Mel,

Thanks for the update.

Thank you also for confirming that you are using the USB C cable as this is typically the most common issue when it comes to this type of situation. Based on your description of the behavior, our next step is to get some additional private information.

Please keep the dock connected to your system (even though not working) and send the output of our diagnostic utility PlugDebug → http://plugable.com/support/plugdebug to us directly via support@plugable.com with ‘For Ticket 418413’ in the subject line. This will allow us match things up and examine some log files from your system to help determine the next steps.

Please also include your Amazon Order ID number for the docking station purchase in your direct email. Please do not post the Order ID or the PlugDebug file in our public forum.

Thank you for giving us the chance to help!

Richard A
Plugable Technologies
https://plugable.com/support

9

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