Can't work out how to generate 2D navmesh on tilemap

Im trying to generate a 2D navmesh on a tilemap ( im following this tutorial 2D Pathfinding in Unity using A* Pathfinding | Towards Dev ), I have set all of the suggested things like layer etc. When I hit scan I see a message scaying took 4ms to complete, but I cannot actually see anything, any ideas?

Do you have a screenshot? (settings + scene view)