So I have most of my game built with BSPs. When I added a Navmesh it seems to only show on the blueprints?
Yes Nav Mesh will work with BSP brushes. What exactly is the problem you’re having? Make sure to turn on Show → Navigation so you can see a live preview of the Nav Mesh while editing your map.
For some reason the green plane that shows the navmesh didn’t appear on the BSP, but it still was a BSP. Maybe a glitch :\
Although the green plane didn’t show it as a navmesh, the BSP still was part of it.
If you could post a picture of the green nav mesh outline and circle what you don’t like it would help understand the problem. Nav mesh boxes can be finicky about how far down they are sunk in the floor, so you can try lowering them.
There was a bug resulting in navmesh not generating initially when navmesh bounds volume was being dragged into a level that already had BSP set up. This is fixed in 4.7.