Target display mode has suddenly stopped working

I've been using display mode target using a cable thunderbolt between my iMac 21.5 inches (end of 2012) and Macbook Air 13 inch (early 2014) for about six months.

I had a few weeks off and had to return to find that I can enter is no longer target display mode! When I press Control-F2 on my keyboard connected to my iMac, that nothing is happening. I also tried Fn-control-F2. I tried different ports in case one of them is damaged. But nothing helped.

Anyone has any suggestions as to why target display mode would have stopped working so suddenly? I really like the feature of double screens between my macbook and iMac and would really like to come back!

Thank you.


I know target Display Mode will work, but only if I use the command-f2 from the login screen. After the connection, the command does not work. have you tried?

Tags: Mac

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