The reason you can’t enter the bridge is the collision mesh is blocking you.
Try opening the static mesh in the Unreal Engine. From there select “Collision”, “Remove Collision”, then use the “Auto Convex Collision” (I used hull count 4, Max Hull Verts 16, Hull Precision 100,000)
This will put collision on the main structures of the mesh but keep the bridge accessible to walk across.
By default the engine will create a simple box collision covering the entire mesh.