THE SHORT ANSWER

Most "no signal" cases come from a cable that does not carry video, the wrong monitor input, a dock topology the Mac cannot use, or a model display limit. Test the monitor directly with a known video cable first, then add the dock back.

Manufacturer documentation · Not physically tested by NYBreaking

Test the shortest path first

  1. Power the monitor on before connecting the Mac, and select the matching input (USB-C, HDMI or DisplayPort) on the monitor.
  2. Connect directly to the Mac with a cable rated for video, skipping the dock or adapter.
  3. Try another Thunderbolt/USB-C port on the Mac.
  4. In System Settings > Displays, hold Option to show Detect Displays if it is offered.

Check the Mac's display limit

Apple publishes how many external displays each Mac supports. A base M1 or M2 MacBook Air supports one; newer models support two with the lid open. If the Mac is already at its limit, an extra monitor stays dark no matter which dock you use.

When the monitor works directly but not through the dock

The issue is the dock, its cable or its topology. A USB-C MST dock may mirror or drop a second screen on a Mac, and a DisplayLink dock needs its driver and screen-recording permission. See why a MacBook mirrors through a dock and dock not detecting a monitor.

Sources you can inspect

Based on official documentation reviewed 2026-10-26. Steps are general; follow the manual for your exact model. No physical test by NYBreaking.

Put the conditions into your own setup.

Choose the exact equipment, then save or print the connection checklist.

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