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When I first set it up, a week ago, this worked fine. This week, it's giving me an instant black screen whenever I plug my HDMI cable into my laptop. What could have changed?
Running Catalina 10.5.6 on a 2017 Mac Pro.
Update: It's working, and I think it had to do with the port on the MacBook I used to plug the cable into. There are four, and apparently just one will work. At least, I hope that's what it is. I discovered this by chance. I need to use it now, so I don't plan to experiment.
Update: It's working, and I think it had to do with the port on the MacBook I used to plug the cable into. There are four, and apparently just one will work. At least, I hope that's what it is. I discovered this by chance. I need to use it now, so I don't plan to experiment.
to get a Mac display to become active, you need the Mac to query the display, and the display to answer with its name and capabilities. Otherwise, the display will not be shown as present, and no data will be sent to the display.
This query is only sent at certain times:
• at startup
• at wake from sleep
• at insertion of the Mac-end of the display-cable, provided everything on that cable is ready-to-go
• on invoking Option-(Detect Display) button in Displays preferences (from another display)
so try doing some of those things and see if the display comes alive.
Modern Displays with multiple ports are sometimes busy scanning the other ports, looking for an input, and miss the query from the Mac. They need to pay attention to the port you are actually using, or they will miss the query.
Some displays have On-Screen Display settings that can be used to tell the display a computer is attached on a certain port, or a certain port should be highest priority. Changing those may make your display more responsive.
Some displays include their own private "sleep" settings for the display alone. This can allow the display to enter its own sleep mode, on top of the Mac's not sending it data. A display that is sleeping on its own cannot respond to the Mac's query, and will stay dark.
Thank you, Grant. Lots of good suggestions, but none that work, I'm afraid. My Vizio TV is very Google-inclined, which may make a difference. It does not have display settings that allow me to do anything other than to name my chosen HDMI port "Computer." I have tried assorted sequences of connection, including doing so just prior to waking up my Mac, doing so when the Mac is already awake. The keyboard shows "mirroring," but does nothing; the screens remain black. I try to be sure the Vizio is awake when I do this. I also went into my Mac's preferences and saw that I could select the TV. But the selection doesn't take. I'm so befuddled as to why this worked last week and the week before and now will not. There could have been a software update in the interim -- I don't always note their passing -- but I don't believe there was.
Mirroring MacBook Pro on TV with HDMI cable
