My external monitor works fine until I unplug my MacBook and connect it again later. Then the Mac doesn’t seem to detect it, and the monitor says “No signal.” Unplugging and reconnecting the cable doesn’t always help, but restarting the Mac usually does. Has anyone had this happen? I’d rather not restart every time I return to my desk.
Not sure which MacBook you’ve got, but last month my MacBook Pro was not connecting to the external monitor after pretty much every replug lol.
When it happens, check System Settings > Displays first. If the monitor’s missing entirely, I’d start with the cable, dock and ports. If the Mac lists it but the screen stays black, then I’d look at the monitor’s input and display settings.
Yeah, it’s completely missing. Just the MacBook screen shows up.
Try holding Option in Displays and see if Detect Displays appears. It shows up in place of the Night Shift button while you hold the key. Clicking it makes the Mac look for connected screens again, so I’d try that before restarting.
If Detect Displays doesn’t help, I’d check the connection path next: the cable, any dock or adapter, and the monitor’s input. That should help narrow down where the connection is failing.
Tried it just now, but nope. The button shows up, but Detect Displays is not working on my Mac, still nothing on the screen.
One other thing to check if it’s a MacBook with Apple silicon: make sure you haven’t accidentally denied the accessory prompt when you plugged back in. That’s how I ended up with my MacBook not recognizing the external monitor once lol. It’s under System Settings > Privacy & Security > Allow accessories to connect.
I’d try a full power cycle on the monitor too. Turn it off, pull the power for a few seconds, then plug it back in and test again. Sometimes that clears a stubborn “No signal”, and it’s an easy one to rule out.
Just tried that. No luck, still says “No signal.”
Is the monitor going through a USB-C dock? If so, try plugging it straight into the MacBook once. That’s probably what I’d try next. If your Mac is not detecting a second monitor only through the dock, that narrows it down to the dock, its cable or the connection between them. If it still doesn’t work directly, I’d check the display cable and the monitor itself next.
Yep, it’s through a dock. Plugged it straight into the MacBook and the picture came back right away.
Ahh nice, there we go. I’d test a different cable between the MacBook and the dock before replacing the dock itself. USB-C cables aren’t all the same, some don’t do video at all, like the white USB-C charge cable a lot of MacBooks used to come with, and others carry video over DisplayPort or Thunderbolt. Yours seems to pass video at least some of the time, but a worn or flaky cable can still drop the signal on and off like that. Grab one that explicitly says it supports video and see if the problem goes away.
Fwiw at work we had one Mac that wouldn’t detect its monitor some mornings, same kind of dock setup, and a new cable fixed it.
Soo swapped that cable and… yep, fixed!! No way, I’ve disconnected the MacBook a bunch of times since and the monitor comes back every time now!