5K iMac video playback problem

[manowar]

I am getting a message when i try and play videos in iTunes (see the screen grab) any help would be great

 

[Paulds38]

hdcp imac 5k

i get this if i try to watch netflix in safari

 

[manowar]

i get this if i try to watch netflix in safari

just tried Netflix and that works

 

[Paulds38]

i get this no external monitor being used

 

[manowar]

weird that i don't get the error when playing Netflix

 

[Paulds38]

iTunes works for me grab don't show film but it working weird hdcp thing