Apple TV 4 - no pictures are streaming from my IMac.

No matter what I tested, no pictures are streaming from my MAC. The TV sees the MAC, it does send music, movies, etc. but no pictures from Photo. None. The wheel starts and spins for hours. I loaded the latest software. There is no firewall. Signal strength is excellent. My apple TV before (versions 1, 2, 3, all showed pictures and for 1 you had to load them) but with 4 nothing.

Please help. Is this a general problem, everyone has?