I just bought the new air with M3 chip, connected 2 external monitors, via a hub (both monitors into HDMI ports on the hub) Hub is plugged into thunderbolt port on air.
if the Air is lid open I get one monitor to be an extended monitor, no issue and the air is the main display. However when I close the lid the second monitor comes on but is identical to the first monitor (main display) and the second monitor doesn’t show up under system settings - display…..
I think that this is an issue with the dock just splitting up the data to both displays and thus let MacBook Air think that there's just one display, not two. Have you tried plugging in both monitors into MacBook Air separately via Thunderbolt? If it then works as it should, you may need to purchase another dock.
I understand that plugging in both displays separately into your Mac would take up all Thunderbolt ports, but you could plug only one display into your Mac so that you can take advantage of the dock's other ports.
Is this a Thunderbolt dock, or just a plain USB-C dock?
My understanding is that Macs do not support attaching two monitors via one host port unless the port is a Thunderbolt port, and the device immediately connected to it is a Thunderbolt device (such as a Thunderbolt dock, some of which have the ability to drive two non-Thunderbolt monitors if the computer supports it).
Because the M3 MacBook Air only supports two monitors when the lid is closed, I don't know whether there may be an additional wrinkle where you have to plug in the second monitor after you close the lid.
Use dual monitors with your MacBook Air with M3 chip - Apple Support
MacBook Air M3 - Dual monitor issue
