El Capitan does not detect my external display

Come on Apple, you can do better. new Samsung monitor not detected by brand new iMac 27" (2015 5k) with capitan. Please get update quickly.

No microsoft fan, but it does work!

I have a MB Air 2015 connected to an ASUS 24" monitor via DVI - DP port. It worked fine with Yosemite.

Since upgrading to El Cap it intermittently will not detect the monitor if I unplug the DP. (i.e., taking my laptop with me on the road).

Today it wouldn't detect the monitor at all no matter how many times I rebooted, reset the SMC, power cycled the monitor.

I tried an HDMI cable and VGA cable with no luck.

I finally saw the post above about disabling user login and enabling auto-login. That seems to have fixed it.

Of course I will have to re-enable this when I take my laptop on the road for security purposes which will be a pain but for now I can use my monitor.

M-

I've just upgraded to El Capitan and now I'm having the exact same issue. HDMI was working fine and now suddenly it doesn't anymore. So I should disable the user loging and enable the auto-login?? I'm not an Apple expert, so can somebody please explain to me how this is done?

Strange thing is that I seem to remember everything was working fine just after installing and the problem only emerged the day after. Is tihis possible? At first I thought it was the hardware. I'm using a Belkin adapter.

I've been a Mac user since the mid 80's so I know my way around the OS. I had the same problem, but on a new MacBook Pro 15". When I booted up, both screens went black with only a white cursor showing. I called Apple Care twice. The first time they had me reset the pram, then reinstall the OS. Still know luck. The second time while I was on hold waiting for a senior tech support advisor, I unplugged all usb devices and the HDMI cable, eventually isolating the problem to the HDMI port. When I did this, the laptop then showed the login page. I logged in, plugged the USB and HDMI devices back in and everything worked fine. When I finally got through to a senior advisor,he had me restart in recovery mode (command + R) and run disk first aid twice. That seemed to have corrected the problem, but after a few restarts the problem reappeared.

Finally, on my own, I switched to auto login and that seems to have corrected the problem, however, when I reboot, the screens are initially "jittery" until the system is fully up.

There is definitely a bug that needs to be corrected between El Capitan and newer hardware. I did not have this problem on my mid 2011 MacBook Pro. I think it has to do with how the startup communicates with certain USB and HDMI devices. Even with disabling the login page, I'm still having a problem with one USB dongle for a Fitbit device

I hope this helps until an OS 10.11 update beyond OS 10.11.1 comes along.

Open "System Preferences" then click on the "Users & Groups"

Then click "Login Options" turn "Automatic Login" on for your user.

Enabling auto login fixed this for me too (well at least so far....). Agree with others that this is only a workaround and not a fix.

My history of this problem:

About a month ago upgraded an MB Pro 15" Mid-2010 (which my wife uses) to El Capitan. Prior to that on Yosemite everything had been working fine with an external Dell U2415 monitor, connected via the Dell provided mini-DP to DP cable (Amphenol cable). I don't recall the exact sequence of events, but the problem of the display not being detected started shortly after that. After messing with it for a long time, eventually purchased another mini-DP to DP cable. Which worked at first, and I thought the problem was corrected, but then came back again shortly afterwards. Seems to be related to the computer going into and out of sleep. The display is not detected when coming out of sleep, nor after that if the cable is removed and reinserted again. Messed with it again for a long time, did the SMC and PRAM resets, re-booting, power cycling the monitor etc., nothing worked.

Then tried a mini-DP to HDMI adaptor cable, and an HDMI cable into the Dell monitor. Started working again. This time we decided to not forcibly put the computer into sleep (i.e. no Apple menu -> Sleep). Worked fine for several weeks, then had to restart the computer yesterday, and the problem came back.

Finally found this thread and tried enabling auto login and now working again, with the mini-DP to HDMI adaptor. Daren't try forcibly putting the computer to sleep, or even try going back to the original mini-DP to DP cable.

The funny thing is that with my main computer, an MB Pro 15" Retina Late 2013, with the exact same model of Dell monitor, U2415, and exact same cables, I have had no problems at all. I also used this computer to verify the other monitor and cables were working when they wouldn't work with the Mid-2010 machine.

And there is a long thread on what sounds like a very similar, if not the same problem, on Yosemite:

Yosemite does not recognize external displays...

But I didn't have problems on Yosemite.

Anyway, the fact that just changing to auto login fixes the problem would appear to point to this clearly being an OS X software problem.

Same exact thing. I had the adapter (branded Isy) which worked just perfectly on an older Macbook (2008), but not on my Pro from 2013. Now I switched to a Hama adapter and it worked as soon as I plugged it into both.

I've also got a Hama mDP to VGA adapter. It's the only one I have and it was working perfectly this morning, as always, with my external display. Now it doesn't. The only thing that changed was the physical location of the display and the computer. The display works fine over HDMI, but not VGA. What the ****?

The laptop does detect the display, though, but gets stuck on 800x600, and I can't change it. It worked perfectly on 1920x1080 (display max) before.

• Retina MacBook Pro 13'' Early-2015 (2.9GHz i5, 512GB SSD, 16GB RAM, if it matters).
• Asus something something, the cheapest I could get with HDMI.
• Some Hama Mini DisplayPort to VGA adapter.

I have had the same issues, and the solution of changing the cable (to mini displayport-display port) and not using the Apple connector also works for me.

I have installed El Capitan in MacBook Air early 2015. My external monitor is Dell P2314H. After the installation, I tried to connected them via mini display port, Apple miniDP to DVI/HDMI/DP connector, and Dell's display port. MacBook Air no longer detected the monitor, and the monitor didn't register any video input from the computer.

I tried to connect via another brand's miniDP to VGA connector, and it worked. I tried to connect my MacBook Air to my HDTV using the same Apple connector via HDMI, it worked. So the culprit must be somewhere between Apple's mini displayport and Dell's displayport. I bought a cheap miniDP-DP cable locally (I live in Jakarta, Indonesia), reconnected the two, and it worked.

I have re-activated log-in in MacBook Air, and it still works.

I hope this helps.

"Also tried to re-detect the display (Settings -> Displays -> hold 'Option' -> 'Detect Displays')"

This worked for me. Thx!

I have a Mid 2011 21" iMac & I was using Thunderbolt to HDMI from Amazon which wasn't detecting the other display. The problem with my situation was just that I didn't pushed the Thunderbolt to hard enough in the socket. Everything works fine now.

This worked for me - I am using Apple LED Cinema Display and I pulled out the plug on the back of the Display and re-seated it hard. It now works!

Any updates on this issue?

Running El Capitan on 6 month old Macbook Pro. Had the issue a few weeks ago, first time I reset the pram, it did nothing. Tried it the following day and the second monitor came back up. Worked for a couple weeks, this morning, the second monitor is not displaying again. I tried SMC Reset, PRAM reset, disabling the login, display settings - detect. Nothing working. I'm running an HDMI viewsonic 27" monitor directly connected via HDMI. I've also tried this same monitor with two other dongles. I've tried this cable and monitor on another system, no problem.

Mac has all updates available.

Exactly the same issue you here, very frustrating. Hoping an update is made available to resolve the display issues asap.

http://osxdaily.com/2014/03/31/detect-displays-mac-os-x/