Target Display Mode between MacBook Pro and iMac won't work I try to use my iMac as a external screen or otherwise if possible, but when I press ⌘ CommandF2 nothing happened. I also try fn⌘ CommandF2 just to be sure

MacBook Pro 2012
iMac 27" 2012

Using Thunderbolt 2
Well, i found out why... I just needed to turn the cable around. For some reason, the Thunderbolt cable can be plugged in the wrong way.