I just purchased a TBT3-UDV, along with a Cable Matters 103046 USB>HDMI adapter and a Plugable DP-HDMI2 adapter. I’m looking to run 3 external monitors on my 2017 Macbook Pro. The monitors are (2) Dell ST2421L and (1) Samsung Syncmaster TV. I hooked up the dock to my mac, then plugged 1 Dell into the Displayport>HDMI adapter using a brand new Amazon Basics HDMI cable. I plugged another Dell into the Cable Matters USB>HDMI adapter with another brand new HDMI cable, then plugged everything into the dock. The Dell plugged into the DP adapter came up right away, but the Dell plugged into the Cable Matters USB adapter did not. I went to the DisplayLink site and grabbed the latest High Sierra drivers, but this did not help. I decided to try a USB-C>HDMI adapter I had lying around (Cable Matters 201014), but plugging this into the Thunderbolt port on the Plugable dock did not work. When I unplugged the Cable Matters 201014 from the dock and plugged it directly into the Mac, the second Dell immediately came up. No matter how I try it, the USB>HDMI adapter seems to be a complete no-go.
So basically, I can’t get my Mac to see more than 1 monitor at a time through the Plugable dock. To get 2 external monitors (while the Macbook is closed), I have to plug one into the dock and one into the Macbook, which defeats the purpose of having a dock. Can you please help me get 3 monitors working? Failing that, at least 2 is a must. Thanks.
For the USB-C to HDMI adapter not working on the second Thunderbolt 3 port, we’ve not tried that specific model here, it’s possible there is a strange compatibility issue. We might want to try sending you one of our USB-C to HDMI cables to see if it works better.
But for the moment, let’s see if we can’t get that DisplayLink adapter up to get you at least two screens going through the dock.
Hello Joshua,
I tried the process in the link you sent about the DisplayLink adapter, but on my Mac, there was no message about a plugin being blocked, and no “Allow” button to click. See this link for the screenshot: https://www.dropbox.com/s/0hwu6w2url7…
This is while the adapter was plugged in. Meanwhile, just to make sure the adapter wasn’t DOA, I plugged it into a Windows PC and it worked fine, so it’s definitely known-good.
So I’m back to where I started. I can only get one display to work through the TBT3-UDV.
I had ordered a Plugable USB-C>HDMI adapter (https://www.amazon.com/gp/product/B01…) last week that just came in, so I can try that through the dock. I’m assuming that’s the one you’d send me.
Sorry to hear no changes. Glad to hear you already had ordered the USB-C to HDMI adapter, that is what I would have tried to send you (or an all in one cable, but the function is the same).
Definitely give that a try and let me know if that is at least working.
For your DisplayLink adapter since it works on Windows and we know the hardware is good, I’d possibly try to uninstall, reinstall, and then immediately check the Gatekeeper is showing the driver blocked then. It’s got to just be a driver issue at this point.
Hello Joshua,
Your hunch about the DisplayLink USB>HDMI was correct. Once we reinstalled and allowed it through Gatekeeper, it worked and has been reliable ever since. Immediately after, we were able to use the Plugable USB-C>HDMI to get 3 monitors working. We rebooted the Macbook, unplugged from dock and plugged back in, and everything worked.
However…the user took their Macbook home over night, and since they’ve come back this morning, we cannot get the Plugable USB-C>HDMI to work at all through the dock. The best we can get is 2 monitors at once, and even that is sketchy. As an example, I unplugged the dock and plugged back in, only 1 of the 2 came up. I tried power-cycling the display that wouldn’t come up but that didn’t work. In System Preferences>Displays>Arrangement, it showed both. When I simply moved the display from one side to the other, it suddenly (seemingly inexplicably) came up.
We are close to giving up on 3 external monitors, but the flakiness of even 2 external concerns me. Is this fairly standard? I feel like for every time the user plugs their Macbook in, there’s a pretty high chance they’ll have to fiddle with something either in System Preferences>Displays or unplugging/plugging monitors in.
Glad to hear that things at least were up and running for a little bit.
I’d like to try and narrow down to see if a particular element is causing these issues. If you are up for it, I’d suggest testing w/ 2 displays at a time in the following combinations: DisplayPort + DisplayLink Cable Matters adapter. If that works normally, try the DisplayPort + USB-C to HDMI adapter.
We may also want to try sending you one of our adapters instead to try in place of one of the Cable Matters adapters to see if that changes anything based on what we find from the aforementioned tests.
We actually tried the Plugable USB-C>HDMI by itself in the dock, with no other displays plugged in, and that didn’t even work.
This isn’t the kind of user who would take their Macbook home and fiddle with drivers, so I really wonder what changed from when it was working the night before, and then the next morning. macOS update?
Any other ideas? I haven’t tried the USB-C>HDMI directly into the Macbook, but I’m not that interested in that anyways, since we want everything running through the dock.
Thanks for the info. That is quite puzzling. I really wouldn’t expect this kind of behavior to happen overnight just from docking and undocking the system. I also would have expected our USB-C to HDMI cable to work through our dock, it does here in our testing with our MacBook Pro systems…
I suppose that an update could have caused this. Do you know if the system perhaps updated from macOS 10.13.2 or is it still on 10.13.1 (which most of our testing is based on)?
