YouTube APi V3 PlaylistItem.insert - forbidden/playlistItemsNotAccessible error

I'm trying to insert into the Watch History playlist using YouTube API v3. I've used the API explorer and authenticated my session.

I enter in the details required and give it my body:

    {"snippet":       {"playlistId": "HLbUVKMjpXy9V9C1R1vpV_8g","resourceId":         {"videoId": "RgKAFK5djSk","kind": "youtube#video"        }      }    }

But then the API Explorer says: You do not have permission to execute this method.

Anyone know how to resolve this issue?