Running MacOS Catalina on a 2019 MB Pro. I had it sitting on a desk connected to an external monitor using a USB-C to Display Port cable and a USB connected keyboard/mouse. With the laptop closed, if I pressed any keyboard key or moved the mouse the system would wake up and Mac OS would show up on the external display. I had to use the laptop remotely for a couple of weeks and just now put it back on the desk and reconnected the Display Port and USB cables exactly as before but it's behaving differently.
It won't wake up with the lid closed. If I open the lid and it wakes up, both the laptop and external displays are active, showing the same Mac OS desktop. It used to be then if I closed the laptop lid the external display would continue but now it goes off with the display briefly showing a No Display Port Signal window. I think before that I used to see this warning but only briefly before the display came back on again. I have Mirror Displays checked in System Preferences. I tried rebooting. I tried disconnecting and reconnecting the Display Port cable at both ends. I tried shutting down and turning on the external display.
The external display works only if the laptop lid is up. Any suggestions would be appreciated. Thanks.
It won't wake up with the lid closed. If I open the lid and it wakes up, both the laptop and external displays are active, showing the same Mac OS desktop. It used to be then if I closed the laptop lid the external display would continue but now it goes off with the display briefly showing a No Display Port Signal window. I think before that I used to see this warning but only briefly before the display came back on again. I have Mirror Displays checked in System Preferences. I tried rebooting. I tried disconnecting and reconnecting the Display Port cable at both ends. I tried shutting down and turning on the external display.
The external display works only if the laptop lid is up. Any suggestions would be appreciated. Thanks.