2019 Macbook Pro running Sonoma. Previously I had connected to this display with a USB-C to DisplayPort cable. Since that port on the display was being used by something else (currently not turned on), I obtained a StarTech USB-C to DVI connector to use another port on the display. When I connected everything, the display was not mirroring the laptop. I went into System Settings / Displays and the display was showing up in addition to Built-In Display. I tried rebooting, reconnecting cables, turning display off and on, using different USB-C ports on the laptop to no avail. The laptop is plugged into a power supply; the cables are securely connected.
Somewhere in my increasingly frustrating attempts to fix this, I chose something like "extend" in a pull down menu and now the external display doesn't even show up in Displays and that pull down menu is not available. If I try to add a display, Apple TV is the only option.
Any suggestions for getting the laptop to recognize and use the external display would be appreciated. Thank you.
Edit: Forgot to mention that I also tried, in System Settings / Displays holding down the Option button and searching for displays.
Update: Tried using my daughter's MacBook Air with same cable and it worked as expected. Just for the heck of it we then connected the cable to my MacBook Pro and lo and behold the external display showed up again and I was able to mirror the laptop to it. How to explain?
Somewhere in my increasingly frustrating attempts to fix this, I chose something like "extend" in a pull down menu and now the external display doesn't even show up in Displays and that pull down menu is not available. If I try to add a display, Apple TV is the only option.
Any suggestions for getting the laptop to recognize and use the external display would be appreciated. Thank you.
Edit: Forgot to mention that I also tried, in System Settings / Displays holding down the Option button and searching for displays.
Update: Tried using my daughter's MacBook Air with same cable and it worked as expected. Just for the heck of it we then connected the cable to my MacBook Pro and lo and behold the external display showed up again and I was able to mirror the laptop to it. How to explain?
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