External Monitor display issue when closing the lid of laptop

"Odd. I sometimes work with my laptop lid closed and using the external monitor, and it's never been a problem. Have you tried updating your graphics drivers? Look in Windows Update under optional Hardware Updates, and see if there's anything relating to your graphics drivers. Since it's a new laptop that's probably not the issue, but it's worth trying.

Just out of curiosity, why don't you use both monitors? I've found that having dual displays is extremely helpful."

See if setting the "Max performance" power plan helps. Also I recommend you to get the latest graphics drivers from Acer's website.

I had the same issue, I found it was fixed once I set my monitor settings to only display on the external monitor.