Sorry for the long post. I have an issue with a sudden lack of DisplayPort signal.
The computer is a 2019 Apple MacBook Pro, 13-inch. 4 USB-C ports.
The monitors are both DELL, a P2715Q and an S2721Q.
The cables are exactly the same, both Plugable USB-C to DisplayPort.
Everything worked fine for months, until two days ago. No system or software changes, no connection changes. No bending or twisting of cables.
Then two days ago I wake from sleep and first one monitor goes dark before lunch. I try switching cables, some flashing and lags almost like a signal is trying to get through, but no change, no signal. Try switching, ports. Still nothing. Completely mysterious. One monitor and one cable work fine on any port. Start a case with Apple and try MSC and PRAM zapping, which fixes it for a day: back to two monitors.
Today both monitors are getting no signal. Escalate the case with Apple and DELL.
With Apple we try SMC, PRAM, and re-installing the OS. Nothing. But we do see all USB-C ports connecting fine to an iPhone (USB-C to lightning) for power and data.
With DELL I do the self-diagnostic tests and call the support folks who confirm the DELL input DisplayPorts are working.
I think that leaves the cables? Any other ideas for fixing? If I had a USB-C to HDMI 2.0 I could test that, but I don’t…
Building on replies to similar topics: the monitors are no longer reported in the USB device tree, and do not show up in the system preferences.
Hi,
There are a few things that we can try like verifying the USB-C to DisplayPort cable is being connected to a computer that it has previously worked with, and that the computer has been restarted after the display stopped working.
Some new computers, tablets, and phones with USB-C ports do not support USB-C video output and are incompatible with this adapter cable.
We also want to be sure that the USBC-DP is connected to the DisplayPort Input for that monitor.
Thank you for double-checking the cable with a previously working computer and monitor so we can get to the next steps.
Richard A
Plugable Technologies
https://plugable.com/support
Thanks Richard, these are useful steps.
On the correct port matter I agree of course. I can confirm that these two monitors only have 1 DisplayPort, and it is for input only. I should have put that in the original message. Sorry for missing that.
The MacBook Pro in discussion is the only computer with which these cables have been used. These cables worked without any issues for months, as did the computer and the monitors. I do not have any other computers that can use these cables.
I can also confirm that the computer (and both the monitors) with which these cables previously worked has been restarted in every configuration and combination of cable (2), USBC port (4), DisplayPort (2), and restart connection order. I would have loved any of those to work, as it would have given me/us (us: Apple, Dell, Plugable, me) some clue as to the nature of the issue.
Hi,
Thank you for the update as well for the detail you provided and the testing you have performed that is much appreciated. Based on your description of the behavior, our next step is to get some additional information about your order so that we can send you a tested replacement for those USBC-DP cables.
Please send us your Amazon Order ID number for the display cables purchase via support@plugable.com with ‘For Ticket 324131’ in the subject line. Please do not post the Order ID in our public forum.
Thank you for giving us the chance to help!
Richard A
Plugable Technologies
https://plugable.com/support
Excellent and clear advice. Thanks. I have sent the email as requested.
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