7 - Player Networking - I cant add observed component

When i try to do it
Back to Unity editor, Select the My Robot Kyle prefab in your assets, and add an observe entry on the PhotonView component and drag the PlayerManager component to it
I get it
PhotonView Detected you dropped a Component missing IPunObservable Interface,
You dropped a <com.MyCompany.PlayerManager> instead. It's been removed from observed field.

Why?