I guess the problem is the door isn’t in reachable area. When i make the NavMeshBoundsVolume visible,i find that whether the door is open or closed, the whole door is always inaccessible unreachable.
As above, also - do they ever show the character actually go through the door in that tutorial?
There is the Can Ever Affect Navigation flag that can be disabled for the some static meshes - like the door. The character would then attempt to walk through the closed door but the collision would stop it. The nav mesh would be unaffected providing its granularity settings are high enough to generate a way through in the first place.
The default collision is simple collision which is a rectangle, so it blocks the character, after i change it to complex collision, the character can walk through the door.