Greetings . . .
I have NOT seen any "traffic" thru the notch of my inner-cover during entire season. My first thought was that the space between the inner-cover and top-cover was too small (notch up), so I turned the inner-cover over (notch down). I am sure the top-cover is pushed foward to provide proper bee-space between front of super and top-cover.
Nothing. The bees just don't want to use it.
Are you sure they know its there? Try sticking your finger in the hole and see if anyones home. I'm sure you can get a bee through that hole one way or another.
Lately we have killed the topic of additonal holes in upper supers, etc. That could be a way to go. I really never notice alot of activity using the top entrance via the inner cover. ikeepbees was right, they do what they want.
Bjorn has the simplest and most practicle method I've seen for getting them to use a top entrance. If you have a hole in every super and everytime you add one you plug the hole in the one below and open the one on the new one then they just keep using a top entrance that just moves up as the hive grows.
It may be that most of them haven't realized it's there, but I'm sure some guard is there.