LoadBalancer health check fails but instance is not terminating

Hello,

I have a load balancer which as you know keeps the health check for the web app/website.

I have deployed nothing in my instance means no app/site so when anyone visits the Loadbalancer URL they see a 502 Bad gateway error which is fine.

and also in the target group, it shows that an instance has failed the health check but the thing is that the auto-scaling group is not terminating the failed health check instance and replacing it.

Below is the Cloudformation code

AutoScailingGroup:
    Type: AWS::AutoScaling::AutoScalingGroup
    Properties:
      VPCZoneIdentifier:
       - Fn::ImportValue: !Sub ${EnvironmentName}-PR1
       - Fn::ImportValue: !Sub ${EnvironmentName}-PR2
      LaunchConfigurationName: !Ref AppLaunchConfiguration
      MinSize: 1
      MaxSize: 4
      TargetGroupARNs: 
        - Ref: WebAppTargetGroup

  AppLoadBalancer:
    Type: AWS::ElasticLoadBalancingV2::LoadBalancer
    Properties:
      SecurityGroups:
        - Ref: ApplicationLoadBalancerSecurityGroup
      Subnets:
       - Fn::ImportValue: !Sub ${EnvironmentName}-PU1
       - Fn::ImportValue: !Sub ${EnvironmentName}-PU2
      Tags:
       - Key: Name
         Value: !Ref EnvironmentName

  Listener:
    Type: AWS::ElasticLoadBalancingV2::Listener
    Properties:
      DefaultActions:
        - Type: forward
          TargetGroupArn: !Ref WebAppTargetGroup
      
      LoadBalancerArn: !Ref AppLoadBalancer
      Port: "80"
      Protocol: HTTP

  LoadBalancerListenerRule:
    Type: AWS::ElasticLoadBalancingV2::ListenerRule
    Properties:
      Actions:
      - Type: forward
        TargetGroupArn: !Ref WebAppTargetGroup
      Conditions:
      - Field: path-pattern
        Values: [/]
      ListenerArn: !Ref Listener
      Priority: 1

  WebAppTargetGroup:
    Type: AWS::ElasticLoadBalancingV2::TargetGroup
    Properties:
      HealthCheckIntervalSeconds: 10
      HealthCheckPath: /
      HealthCheckProtocol: HTTP
      HealthCheckTimeoutSeconds: 8
      HealthyThresholdCount: 2
      Port: 80
      Protocol: HTTP
      UnhealthyThresholdCount: 5
      VpcId:
        Fn::ImportValue:
            Fn::Sub: "${EnvironmentName}-VPCID"