EDIT: Looks like this may be a bug, I solved the problem by restarting the editor. The nav mesh was properly regenerated and allowed movement between rooms, but the NavMesh view still showed the brush. I restarted the editor and it disappeared and the NavMesh view renders everything correctly.
Was doing some level design this morning, however navmash thinks there is a blocking brush in between my two rooms. When I started this morning, there was a brush there which I added a subtractive brush to for the doorway. I noticed the navmesh wasn’t being generated for the doorway so I deleted the wall and the subtractive brush, however the navmesh still thinks there is a brush there. I’ve tried deleting the navmesh volume and the RecastNavMesh actor to no avail. I also tried “Rebuild Geometry”. Any idea how to fix this or what’s causing it?