MacBook Air screen blank, unable to connect to external monitor

See if the following can help:

1. Connect your external monitor with a USB-C → HDMI/DisplayPort cable (direct is best, avoid cheap hubs).
2. Plug in power, plus a keyboard and mouse (wired or Bluetooth paired previously).
3. Close the lid — this should trigger Clamshell Mode and force the Mac to use the external display.

If nothing shows, try a full shutdown (hold power until it turns off, wait 30s, then turn back on).

If still blank, try holding the power button at startup until you see (or should see) Options — even if you can’t see it on the broken screen, sometimes this forces a signal out to the external monitor.

If none of that works, it may point to an issue beyond the display panel — possibly with the display circuitry that also drives external output. At this point you will need to contact Apple Support directly for further assistance with this matter. To do so, simply select the "Support" link on the lower left-hand side of this forum's web page.

I have no idea if this will work, but try to connect the display to the computer, then wait a few seconds, and then press the Return key.