AWS ALB + ECS + gRPC + Ruby "Trying to connect an http1.x server"

Question

I am building gRPC　server with Ruby and trying to request it from Ruby Client through AWS ALB. We deploy it to AWS ECS on Fargate

problem

When I try to send requrest throgh ALB, I got the error below

GRPC::Unavailable (14:failed to connect to all addresses; last error: INTERNAL: 
ipv4:myip:50051: Trying to connect an http1.x server. 
debug_error_string:{UNKNOWN:failed to connect to all addresses; last error: INTERNAL: 
ipv4:myip:50051: Trying to connect an http1.x server {grpc_status:14, 
created_time:"2023-08-04T19:03:50.762448829+09:00"}}):
[6edb224a-1729-49ae-aa15-d396e4e04366] 
GRPC::Unavailable (14:failed to connect to all addresses; last error:
 INTERNAL: ipv4:myip:50051: 
Trying to connect an http1.x server. 
debug_error_string:{UNKNOWN:failed to connect to all addresses; 
last error: INTERNAL: ipv4:myip:50051: 
Trying to connect an http1.x server 
{grpc_status:14, created_time:"2023-08-04T19:03:50.762448829+09:00"}}):

I use CDK to build Cloud and the code is like this

    const alb = new ApplicationLoadBalancer(scope, 'alb', {
      internetFacing: true,
      http2Enabled: true,
      loadBalancerName: `alb`,
      securityGroup: this.sgGroups[0],
      vpcSubnets: {
        subnets: this.subnets,
      },
      vpc: this.vpc,
    })
    const tg = new ApplicationTargetGroup(scope, 'a', {
      protocol: ApplicationProtocol.HTTP,
      protocolVersion: ApplicationProtocolVersion.GRPC,
      port: 50051,
      targetType: TargetType.IP,
      vpc: this.vpc,
      healthCheck: {
        healthyGrpcCodes: '0-99',
        port: '8080',
        path: '/grpc.health.v1.Health/Check',
        protocol: Protocol.HTTP,
      },
    })
    new ApplicationListener(scope, 'b', {
      loadBalancer: alb,
      protocol: ApplicationProtocol.HTTPS,
      port: 50051,
      certificates: [
        {
          certificateArn: certificate.certificateArn,
        },
      ],
      defaultTargetGroups: [tg],
    })

What I confirmed

• gRPC server works fine becaseuse I got resepose when I attached domain to Fargate Task public IP without ALB and request it with ruby client.
• ALB Health Check status is healthy
• I checked security group, and it looks fine. they allow 50051 and 8080 request from anywhere.
• I found similar problem on StackOverflow url, but it doesnt work for me.

I will be very happy if someone has know something and let me know.