2021 Macbook Pro HDMI port no longer working

The Mac uses a system that reminds me of “Plug and play” to determine what display is connected, and what its capabilities are.

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

• hold the Option key while you click on the (Detect Display) button that will appear in Displays preferences (from another display)

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

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if no joy, please post a link to the specs for the display, and what cables you are using.

That model natively supports:

Display Support

Simultaneously supports full native resolution on the built-in display at 1 billion colors and:

• Up to two external displays with up to 6K resolution at 60Hz at over a billion colors (M1 Pro)

That is the limit of fully hardware-accelerated displays.

If you wish to support additional displays (without hardware acceleration) you can use a DisplayLink Docking device. The Dock you cited is such a device.

What may have happened is that a recent software update clobbered your DisplayLink Driver software. The device-maker or DisplayLink may have an updated version available.

EXACTLY what model 2021 MacBook Pro 16-in do you have? especially PRO Processor or MAX Processor?

Samsung looks to be (2) 4K display with HDMI 2.0 and DisplayPort inputs.

your graphics/tablet looks to be 1920 by 1080 with a USB interface.

if a dock is involved, what dock?

¿what is connected to what?

it would be very unusual to successfully convert to anything else except DVI starting from HDMI at the computer end.

For your 1920 by 1080 graphics/tablet, that resolution could fit on a USB-C cable.

Wait, what?

all displays connected to that one Dock?