2018 MacBook Pro Target Display Mode Not Working

Yep I hadn't tested this as having sound at work was never necessary. I've just tested now and annoyingly this is not working. I have sent feedback to Apple via the portal I downloaded when signing up via the Beta testing...I don't understand how this can be so hard when all was working perfectly in Sierra 😟 hoping this gets fixes ASAP

Did not solve the problem for me. 2018 MBP 15 with mid 2011 27" iMac, using

thunderbolt on iMac to thunderbolt on USB-C docking station on MBP.

Just upgraded to mojave 10.14.2. My iMac (high sierra) does nothing. Doesn't seem to

recognize key strokes at all. Tried all the suggestions. Original

bluetooth keyboard no longer works. Have McCally wired replacement with

identical mac keyboard. Tried original anyway. Nothing. Aargh!

and the list of "if it does not work" from the article are all does not apply?

If Command-F2 doesn't work

If your iMac doesn't switch to Target Display Mode when you press Command-F2, check these things:

• Make sure that the iMac you're trying to use as a display supports Target Display Mode. 
• Target Display Mode works only when your primary Mac is logged in to a macOS user account. For example, if your first Mac is at the FileVault login screen, pressing Command-F2 on your iMac does not enable Target Display Mode. You must first log in to your Mac (using a regular display, if necessary) before you can use an iMac in Target Display Mode.
• Make sure that you're pressing Command-F2 on the keyboard that's connected to the iMac you want to use as a display.
• In Keyboard System Preferences, if the checkbox is enabled for "Use all F1, F2, etc. keys as standard function keys," the key combination changes to Command-Fn-F2.
• Make sure that your Mini DisplayPort or Thunderbolt cable is connected to both computers.
• If you're currently logged in on the iMac you want to use as a display, try logging out to return to the login window. Then press Command-F2 again.
• Some older Apple keyboards and third-party keyboards might not allow Command-F2 to toggle display modes. If this happens, use the keyboard that came with your iMac to toggle Target Display Mode on and off. 
• If your iMac is currently started up in Windows, it won't enter Target Display Mode. Target Display Mode isn't supported in Boot Camp.

I have Mojave 14.3 on both a brand new MBP 2018 and a late-2012 iMac. I just got the needed TB2-TB3 adaptor and when I plug the two machines in and hit CMD-F2 on the iMAc the screen goes black and will not come back until I unplug the TB cable from it. Mojave has not solved anything in my personal experience. Glad it did for many, but this is frustrating, given I contacted support and read all the official apple pages on this prior to buying the cables and it seemed it would be fine.

Has anyone else had luck using the most recent Mojave version, 14.3?

No idea, as I only have the one MBP. My last one was a 2008 model that died years ago. BUT updated to add that while on the phone with a USELESS tech support person today it worked. Maybe it was her screen-sharing with me that pushed it over the edge? So random.

one note: on my mac, despite having my Function keys set to their F1, F2, etc. setting i STILL need to hit CMD+FN+F2. CMD+F2 alone does nothing. AND I need to hold the three keys down for about a second for it to work. I'm still not convinced this is going to work reliably going forward, but I'm happy for today at least.

Hi katbay, Thanks for advice! I have tried with Mac USB and BT Keyboards. They are the same ones that used to work for connecting Target display for 2+ years.

It is good to know that you have similar setup. I spoke to tech at the Apple Store, who told me they were having trouble with this particular model of MBP - am unsure if they meant Radeon GPU or just the 2018 model in general.

Thanks again.

I have a iMAC (27-inch, mid 2011) runs on macOS High Sierra version 10.13.6 and MacBook Pro (15-inch, 2018) runs on macOS Mojave 10.14.3. and connects the two using Apple Thunderbolt 3 (USB-C) to Thunderbolt 2 Adapter. I could report that the target display mode is now working. I am so happy that Apple listened and fixed the problem. THANK YOU APPLE. You are the best.

Same here. 13-in 2018 MBP to Late-2013 iMac 27", via TB2 and USB-C adapter, all-Apple from one end to another, running 10.14.5 everywhere. Sometimes, my iMac will blackscreen me if I'm logged in, and sound won't go through the iMac speakers (the option is selected but noting will come out.

Mind you, the iMac went through its share. Right now, even with my RAM upgrade, it can't seem to sync my iCloud drive and Time Machine at the same time. Also, I'm not sure if I have the original keyboard (moved twice since I got it), but I tried with a wired extended keyboard too, to no avail. Could it be that the iMac will blackscreen me if it's too busy?

tried two different Thunderbolt 2 - USB-C adaptors.

What Make&Model are these?

one is hooked up to a regular monitor and is working great.

I can attest to this also. USB-C/Thunderbolt3 -> DisplayPort works as expected.

Anyone tried:

StarTech.com Thunderbolt 3 to Thunderbolt 2 Adapter

Maybe this one works.

They solved this problem. If you update the system to the newest macOS Mojave Beta 10.4.1, then you are fine with the target display mode.

REAL (not Beta) 10.14.1 was released Tuesday, 30 October 2018.

ThunderBolt-3 to -2 cable.

A dock may re-drive the signals, you need a direct connection.

If you only want to hold the CMD-F2 keys, you can go to system prefs > keyboard > select "use F1, F2, etc. as standard function keys"