Hi, did you try to visualize the navmesh (Navmesh Content Examples | Unreal Engine Documentation) the AI uses and confirm that it generates inside the walls? Since the AI only uses the navmesh for navigation that means that if the wall blocks navmesh generation, then the AI won’t move through that.
As for seeing through the wall needs to ignore the collision channel that AI sight sense uses (Visibility by default but you can change that in the project settings).