Nevermind, i found a fix for it
Thanks to neilb41 for the fix.Re: my macbook pro does not detect external display anymore
I hesitate to add to such a long thread but after weeks of frustration (and suffered ridicule when I could not use my Mac to support a presentation!!) I finally stumbled on a simple solution.
I had previously repaired permissions without apparrent success but I would recommend doing this as poart of good housekeeping anyway. Then I reset the PRAM. PRAM holds a number of system settings while your computer is switched off... including the display settings. To do this (copied from http://support.apple.com/kb/ht1379)
- Shut down your Mac.
- Locate the following keys on the keyboard: Command (⌘), Option, P, and R. You will need to hold these keys down simultaneously in step 4.
- Turn on the computer.
- Press and hold the Command-Option-P-R keys before the gray screen appears.
- Hold the keys down until the computer restarts and you hear the startup sound for the second time.
- Release the keys.
Worked for me first time. I wonder why Apple could not have suggested that as a reply to the thread!!
I have tried this process twice and it still will not detect my external monitor. I am lost for ideas and have tried every thread available. Sending mine in to the Apple store today to fix this problem I use my external monitor for coding and its hard on the eye sight when using this one on the Macbook Pro.
For what it's worth: I had similar problems: I have a Mac Pro (2,1) with a 5770 graphics card. The card supports three displays (one DVI, two DP ports). I have two 30" cinema HD displays connected to it and one AOC 24" FullHD monitor via DP.
Quite frequently, the AOC would not be recognised when waking from sleep and I had to force the computer to detect it (unplugging cables, etc.). Given that the Mac Pro is about 7 or 8 years old, I changed the 3V Lithium backup battery (Panasonic CR 2032). That changed it completely and I haven't had any more problems.
Give that a try.
I don't know if this will help, but it just worked for me.
My issue was not related to an update or anything.. It just seemed both my office and home external monitors stopped being recognized.
So frusterated I just switched the ends of the HDMI to the mini-dv adaptor / monitor, and it popped right onscreen like before. Wierd, but something to try if you are desparate!