I started navmeshing my world space by hand but there are some spots on the land that no matter what I do the navmesh refused to go it's like hitting a brick wall and just stops and wonts to go in a different direction what would course this ?

I would also like to know this, I've also had this issue and couldn't figure out what was causing it.

You're at a cell border. In the cell view window while in an exterior, hit 'B' and you'll see thin yellow lines where one cell stops and the other begins. You need to have NAVM vertices on both sides of the border lined up so that, when finalizing, the line segments are flush and become thick green bars signifying properly linked NAVMs.

Ok thanks