检查以下方面：

1. 检查CloudFront分配给Application Load Balancer的端口和协议设置是否正确。

2. 重新检查Application Load Balancer的目标组配置是否正确。

3. 确保Application Load Balancer和CloudFront都使用相同的证书。

示例代码：

Resources:
  MyLoadBalancer:
    Type: AWS::ElasticLoadBalancingV2::LoadBalancer
    Properties:
      Type: application
      Subnets: 
        - subnet-XXXXXXX
        - subnet-XXXXXXX
      SecurityGroups:
        - sg-XXXXXXX
  MyTargetGroup:
    Type: AWS::ElasticLoadBalancingV2::TargetGroup
    Properties:
      Port: 80
      Protocol: HTTP
      VpcId: vpc-XXXXXXX
      HealthCheckIntervalSeconds: 30
      HealthCheckPath: /index.html
      HealthCheckProtocol: HTTP
      HealthCheckTimeoutSeconds: 5
      HealthyThresholdCount: 2
      UnhealthyThresholdCount: 2
      Matcher:
        HttpCode: '200'
  MyListener:
    Type: AWS::ElasticLoadBalancingV2::Listener
    Properties:
      LoadBalancerArn: !Ref MyLoadBalancer
      Port: 80
      Protocol: HTTP
      DefaultActions:
        - TargetGroupArn: !Ref MyTargetGroup
  MyCloudFrontDistribution:
    Type: AWS::CloudFront::Distribution
    Properties:
      DistributionConfig:
        Origins:
          - Id: !Ref MyOrigin
            DomainName: !GetAtt MyLoadBalancer.DNSName
            CustomOriginConfig:
              HTTPPort: 80
              HTTPSPort: 443
              OriginProtocolPolicy: http-only
        Enabled: true
        HttpVersion: http2
        IPV6Enabled: true
        PriceClass: PriceClass_100
        Aliases:
          - mydomain.example.com