'09 iMac & Retina Pro Target display mode

[iamthewalrus007]

I'm trying to use a 2009 iMac at school (equipped with a MiniDisplay port) in Target display mode with my Retina Pro. Turned both machines on, connected them, tried the Command + F2 and also Command + Fn + F2 but still nothing.

Any explanation on why this isn't working? Or how I can correct the issue?

Thanks for your help!

 

[KylePowers]

Are you pressing Command + F2 on the iMac keyboard or the MBP keyboard?

 

[iamthewalrus007]

Tried from both but started with iMac keyboard, since I wanted the Retina to display on the iMac