Am I doing this correctly? Clamshell mode

[TimDeRosa]

I want to connect my M1 MacBook air to an external monitor. Monitor's connection is HDMI and I am connecting this to my MacBook Air using an Apple AV multiport display adaptor, power is connected to MacBook Air as well. I have no trouble connecting to the monitor with the display open and then shutting it, but I want to be able to connect with the display closed and not have to open it each time.

I checked to make sure my setting "prevent automatic sleeping when on power adaptor" is on as well. Am I missing something? My software is all up to date.

 

[mzeb]

What external mouse and keyboard are you using? Clamshell doesn't work without those being recognized. Both bluetooth and usb should work but usb is more consistent. Also, the setup won't start up automatically if you are using bluetooth mouse and keyboard and plug in the AV Adapter. You'll have to tap a key on the keyboard or mouse to make the computer wake up.

The only other thing I could think of would be the HDMI cable. If it isn't up to spec it might work just fine out of clamshell mode but it might not be recognized when the lid is closed. If it's a cheap cable sometimes they aren't certified by the HDMI consortium and don't necessarily have all the features.

 

[FreakinEurekan]

It works connecting my M1 Max MBP with lid closed. I'm using LG 5K display (also powers the Mac via Thunderbolt) and an Apple Magic Keyboard and Magic Mouse.

 

[mk313]

Agree with mzeb. If you have a USB mouse or keyboard, try plugging one of those in & see if hitting keys/ tapping the mouse causes the computer to wake from sleep. If it does, then it could be the mouse/keyboard that is the issue. If not, then I'd suspect the video cable.

FWIW, my laptop turns on just fine in clamshell mode & I didn't do anything special in settings. It usually takes a couple of taps on the mouse or keyboard to wake it though. I'm running through a dock, so USB-C to the dock, then HDMI from the dock to both external monitors.