Experienced same issue today after owning my 2021 MacBook Pro M1 for 3 days. Monitor was not detected after a reboot. Here's my set up: LG 32UN880-B - https://www.lg.com/us/monitors/lg-32un880-b-4k-uhd-led-monitor Monterey 12.2.1 Steps I tried to get this to work again...switched monitor input to HDM1 and DisplayPort then back to USB-C which still didn't work. Power off the monitor and unplug USB-C cable from laptop. Plugged it back in and power on the monitor and she's back! So glad it's working again otherwise it'll kill my productivity for a long time. I did install Monitor Control app yesterday to adjust my LG monitor screen brightness and volume (LG OnScreen Control app is so buggy even after the recent release) so I was wondering if a 3rd party app cause this issue. For others, I would recommend to disconnect everything and try SMC or PRAM reset then reconnect everything to see if it's able to detect again.