Marshmallow pop up not working

[CarlosSW]

Hi. So I kept hearing about marshmallows... Peeking notifications and actually got excited about it. Looked forward to it as I am constantly missing notifications on lollipop. I got marshmallow... And there is NO Peeking but something called previews in pop up... THAT DONT Work. I have it on and now when I get an email... No preview in the bar at top. Just an email icon. Please help... Im ready to Chuck this thing