I have two USB-C monitors (specifically Dell P2219HC), and I am trying to connect to them both as separate external displays. I am using the included USB-C to USB-C cable for each monitor.

If I plug one in, in any of the 4 Thunderbolt ports, it connects to it just fine. If I plug the second one in, in any of the 3 remaining ports, it does not detect the monitor, and the monitor displays a message indicating that there is no USB-C signal from my device. And vice-versa. I am not sure why this is happening.

I am running macOS High Sierra 10.13.6, my graphics card is the "Intel Iris Graphics 550 1536 MB".

  • What cables are you using in each monitor?
    – Allan
    Oct 2, 2018 at 18:51
  • I am using USB-C to USB-C for each, I have added this to my question.
    – Abraham
    Oct 2, 2018 at 18:52
  • The ones that came with the monitor or generic ones. If one of them works, try swapping the cables.
    – Allan
    Oct 2, 2018 at 18:58
  • They came with the monitors. They both work independently, but it doesn't work when I try to use them both at the same time.
    – Abraham
    Oct 2, 2018 at 19:01

2 Answers 2


I have tried again today, and after plugging the monitors in and out, it works as expected now... I am not sure why this happened. Perhaps my macbook detected one of them as a display and the other as a charger instead of a display? I am not sure.

  • Sound like some bugs or incompatibility. If it always happens, you can try one USB-C - USB-C connection and another USB-C - DP connection.
    – amdyes
    Jan 31, 2019 at 6:03
  • It was weird... At the time I tried different combinations of two ports on my laptop, and occasionally it would work, sometimes not. After it started working, afterwards it was fine and I've had no problems since then. My guess is it took a few tries to get it to recognize both as monitors, etc, and then kept the configuration afterwards. Something like that.
    – Abraham
    Feb 1, 2019 at 18:22

Late to the party here--but I believe you should be able to daisy chain these monitors together, and thereby just use 1 usb-c cable to connect your MacBook Pro (MBP) like so:

1: MacBook Pro:any port -> USB-c -> Monitor "A":USB-c 2. Monitor "A": DisplayPort (out) -> Monitor "B": DisplayPort(in).

I'm interested to know if this daisy chaining method works. This "should" work as Mac OS and the monitors both support DisplayPort 1.2 MST (multi-stream transport), but would love to hear if it does in real life.

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