Dell U4021QW not connecting via Thunderport

Macbook Pro M1 Max with Dell U4021QW monitor. CANNOT get a display from Thunderbolt port. Only HDMI. Both devices have latest firmware (as of 02-03-21). Downloaded Dell Display Manager with latest update. Tried multiple cables on all ports. What am I missing? Very frustrating.

MacBook Pro 16″, macOS 12.1

Posted on Feb 3, 2022 7:50 AM

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Posted on Feb 3, 2022 1:07 PM

The one with the ThunderBolt is likely to be a ThunderBolt "Pro" cable. Any full-speed ThunderBolt cable over a half-meter requires it be an ACTIVE cable, that has signal re-drivers in it. If you bought a new one of those from Apple, they charge US$129.


That you can get something from HDMI suggests the display may be working.


The ThunderBolt INPUT port is the one next to the audio jack, in the middle of all the jacks, near the HDMI ports. The one at the end is a USB output.


to get a Mac display to become active, you need the Mac to query the display, and the display to answer with its name and capabilities. Otherwise, the display will not be shown as present, and no data will be sent to the display. "No signal detected" is generated by the DISPLAY, not by the Mac.

 

This query is only sent at certain times:

• at startup

• at wake from sleep — so momentarily sleeping and waking your Mac may work

• at insertion of the Mac-end of the display-cable, provided everything on that cable is ready-to-go

• on invoking Option-(Detect Display) button in Displays preferences (from another display)

 

so try doing some of those things and see if the display comes alive.




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Question marked as Top-ranking reply

Feb 3, 2022 1:07 PM in response to MacHoBe

The one with the ThunderBolt is likely to be a ThunderBolt "Pro" cable. Any full-speed ThunderBolt cable over a half-meter requires it be an ACTIVE cable, that has signal re-drivers in it. If you bought a new one of those from Apple, they charge US$129.


That you can get something from HDMI suggests the display may be working.


The ThunderBolt INPUT port is the one next to the audio jack, in the middle of all the jacks, near the HDMI ports. The one at the end is a USB output.


to get a Mac display to become active, you need the Mac to query the display, and the display to answer with its name and capabilities. Otherwise, the display will not be shown as present, and no data will be sent to the display. "No signal detected" is generated by the DISPLAY, not by the Mac.

 

This query is only sent at certain times:

• at startup

• at wake from sleep — so momentarily sleeping and waking your Mac may work

• at insertion of the Mac-end of the display-cable, provided everything on that cable is ready-to-go

• on invoking Option-(Detect Display) button in Displays preferences (from another display)

 

so try doing some of those things and see if the display comes alive.




Feb 4, 2022 8:06 PM in response to Grant Bennet-Alder

The Thunderbolt 4 cable supplied with the monitor is actually active and works with another monitor just fine (as well as all the ports on the MacBook).

After much back and forth with Dell they provided new firmware, drivers and DDM to load from a PC.

This actually worked. The second I connected the cable after this it worked exactly like it should.

Thanks to all who tried to help!

Feb 3, 2022 10:11 AM in response to MacHoBe

Please input your monitor to the correct input.

Next navigate to the top left of the screen on your mac. You should see the apple logo,

next click the apple logo

 > About This Mac > Displays tab (second tab)

Make sure to see that your display is showing here. You can mess with the display preferences to see if it shows in a different resolution. It might be that apple display driver cannot handle the onboard display with several other displays. Have you attempted plugging in the power along with a keyboard and mouse (or bluetooth) and shutting the lid. It might be too many resources for macbook to handle.

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Dell U4021QW not connecting via Thunderport

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