Macbook Air 15: No External Display When Lid Closed with Power

I have a Macbook Air 15". When connected to an external monitor, I lose the display when I close the lid. Power cord is plugged in. External display shows when lid is open, but cuts off when I close the lid. Display set to never turn off when on power. Already did a total reset. Still happening. I have an older M1 Macbook Air that displays fine in clamshell and this computer used to work until an update a couple months ago. Weird. Can't figure it out. Any suggestions appreciated.