Dell Monitors/HDD not detected

I have a MacBook Pro (15-inch, Late 2016). I have 2 Dell U2515H as well as an external HDD attached to the dock that are not being detected. The keyboard I have plugged into the dock is being detected and sound is getting passed through the dock.

The monitors are connected via DisplayPort to mini DisplayPort cables. I have tried connecting the HDD via one of the usb ports, as well as a usb-c port with no success.


I’m having the same problem with two Acer monitors and a MacBook Pro 2019. I’ve tried connecting and the monitors aren’t detected. Power delivery is working but not the monitors. Need assistance.

I saw a suggestion in another thread that the apple power cable wasn’t Thunderbolt 3. I have switched the cable to the included cable and now both monitors and the HDD connect.

One of my monitors color is now extremely yellow tinted though, so I continue to troubleshoot that. I can create a new thread for that issue.

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Sorry to hear about the display issues. As @mikekellyio pointed out, please do ensure that you are using the original Thunderbolt 3 cable that came with the dock. Not all Thunderbolt 3 and USB-C cables provide the same functionality, as they aren’t created equally.

If you are indeed using the original Thunderbolt 3 cable, could you please let me know the specific make and model of your Acer monitors?

Thank you!


Hello. Thanks for your response. I used the Plugable Thunderbolt 3 cable that came with the document. I’m wondering if the DisplayPort adapters that I’m using are the problem. I saw on an FAQ page that not all adapters work. Any advice there?

Could you please provide the make and model (or a direct web link) to the DisplayPort adapters you are using?

These adapters need to be “active” adapters in order to work properly with our TBT3-UDC1 docking station. If they are “passive” adapters, then they will not work at all.

Thank you!


I ended up purchasing two “active” DP adapters and that did the trick. I am fully operational. Thanks!

Great! Thanks for the update.

I’ll be closing this topic, but please feel free to open a new post or reach out to us at for any other questions or concerns. We’re glad to help.

Best wishes,