Q: Upgraded to 10.11.6 - now monitors don't work

I'm having a pretty similar issue. Updated to OS X 10.11.6 (15G1004) using a Mac Pro (Early 2009). Right away I was informed nvidia web driver (346.03.15f02) was not compatible and its using the default OS X graphics driver. I had no idea this update was this new otherwise I wouldn't have done it. This machine is already pretty wishy-washy. Taking a screenshot doesn't work correctly, so I had to take a picture externally. The background images are the exact same as well.

Monitors are HP L1906 (Left) and DELL P2212H (Right). LED Cinema Display works just fine. At the moment I'm at work, IT guys have no idea. I'm thinking its the nvidia driver thats needed but I don't know how long that'll be. Thinking about rolling back to 10.11.5 but not 100% sure if that'll the best option. I work as a video editor so the colors being off is a huge problem.

Any suggestions?

Same problem here:  I upgraded 2 MacAir to 10.11.6 (intel Graphic 5000 , 1536MB) and now Thunderbolt Display does not work.  Reset PRAM, SRC, changed to another Thunderbolt display:  Not recognized by El Capitan.  I then hooked up an old ASUS monitor with a Thunderbolt adapter and this worked.   Please help. Thank you

Hi,

I had the exact same problem (MB pro, mid-2014, 13" Retina, apple display 27" thunderbolt)

Apple assistance solved my problem on the phone by reinitializing PRAM and SMC chip

First step: PRAM reset

Turn off computer. Make sure the computer is plugged with the sector

Reboot with shift-ctrl-alt buttons pressed before you press on the power button. keep the power button pressed for 5 seconds. Nothing will happen visually (for me, apparently for some it can turn the green light of the Magsafe to Orange)

Then turn on your computer

Second step: SMC ship reset

Turn off again the compiter

Reboot with atl-cmd-P-R button (piano helps) pressed before you press on the power button. Once youve pressed the power button, keep the other buttons pressed. This will keep rebooting the computer: Do this 3 times)

Once you've released the atl-cmd-P-R buttons, it will turn on the computer as usual.

Now try to plus your thunderbolt apple display ! should work

*Update*
I had tried resetting PRAM and SMC chip with no new result.
But...
My problem was completely fixed after installing the latest newly released NVIDIA driver (346.03.15f03).
Colors are back to normal and I can go back to watching non-blue people on youtube at work. ;D

Upgraded over the Weekends and had the exact same problem, when I plugged it in a Thunderbold Screen at my office. It's not my private computer so I was a "litte bit" nervous about the issue that occured

Did step one an restarted PRAM. After turn it back on it automatically worked again!!

Thank you for the tipp. I thought I was trolled by life

Thanks for your information mofolaz, it work!