BodyDetection in ARKit

Here is my code. I don't understand why it doesn't work, please help me

import SwiftUI
import RealityKit
import ARKit
import Combine

var character: BodyTrackedEntity?
let characterOffset: SIMD3<Float> = [-1.0, 0, 0] 
let characterAnchor = AnchorEntity()

struct ContentView : View {
    var body: some View {
        return ARViewContainer().edgesIgnoringSafeArea(.all)
    }
}

struct ARViewContainer: UIViewRepresentable {
    

    
    func makeUIView(context: Context) -> ARView {
        
        let arView = ARView(frame: .zero)
        arView.setupARConfiguration()
        arView.loadbody()
        arView.scene.addAnchor(characterAnchor)
        return arView
        
    }
    
    func updateUIView(_ uiView: ARView, context: Context) {}
    
}

extension ARView: ARSessionDelegate {
    
    
    func setupARConfiguration() {
        let configuration = ARBodyTrackingConfiguration()
        self.session.run(configuration)
        self.session.delegate = self
    }
    func loadbody(){
        var cancellable: AnyCancellable? = nil
        cancellable = Entity.loadBodyTrackedAsync(named: "robot.usdz").sink(
            receiveCompletion: { completion in
                if case let .failure(error) = completion {
                    print("Error: Unable to load model: \(error.localizedDescription)")
                }
                cancellable?.cancel()
        }, receiveValue: { (character: Entity) in
            if let character = character as? BodyTrackedEntity {
    
                character.scale = [1.0, 1.0, 1.0]
                cancellable?.cancel()
            } else {
                print("Error: Unable to load model as BodyTrackedEntity")
            }
        })
    }

    
    public func session(_ session: ARSession, didUpdate anchors: [ARAnchor]) {
        for anchor in anchors {
            guard let bodyAnchor = anchor as? ARBodyAnchor else { continue }

            let bodyPosition = simd_make_float3(bodyAnchor.transform.columns.3)
            characterAnchor.position = bodyPosition + characterOffset

            characterAnchor.orientation = Transform(matrix: bodyAnchor.transform).rotation
   
            if let character = character, character.parent == nil {

                characterAnchor.addChild(character)
            }
        }
    }
}


#if DEBUG
struct ContentView_Previews : PreviewProvider {
    static var previews: some View {
        ContentView()
    }
}
#endif