I updated my MacBook Pro 2015 model to Monterey last week and the external monitor was working for some days. Today when I disconnected and connected again it stopped recognizing the external display at all. All the tips of making the Detect Display button visible by holding OPT button does not work.
I have tried restarting the Mac, logging out, changing the port, external display detection not working for me anymore. This is a serious failure for my productivity.