title: grpc method call error: Failed to pick subchannel
body: <p>gRpc Client:
  Python:3.8
  grpcio: 1.38.1</p>
  <p>gRpc Server:
  Dotnet core 5.0
  LoadBalancer
  AKS: 1.19.7</p>
  <p>I'm getting below error when my python client calls a method.
  Any help to resolve is really appreciated.</p>
  <p>Python code snippet</p>
  <pre><code>with open('chain.pem', 'rb') as f:
          trusted_certs = f.read()
  
  credentials = channel = grpc.ssl_channel_credentials(root certificates=trusted_certs)
  
  # 10.200.3.24 is the K8S service IP with 3 replicas
  channel = grpc.secure_channel('10.200.3.24:443', credentails, options=(('grpc.enable_http_proxy', 0),))
  
  stub = query_pb2_grpc.QueryStub(channel)
  
  empty = google_dot_protobuf_dot_empty__pb2.Empty()
  data = stub.TestMethod(empty)
  
  </code></pre>
  <p>error</p>
  <pre><code>_InactiveRpcError: &lt;_InactiveRpcError of RPC that terminated with:
      status = StatusCode.UNAVAILABLE
      details = &quot;Empty update&quot;
      debug_error_string = &quot;{&quot;created&quot;:&quot;@1625180429.368158115&quot;,&quot;description&quot;:&quot;Failed to pick subchannel&quot;,&quot;file&quot;:&quot;src/core/ext/filters/client_channel/client_channel.cc&quot;,&quot;file_line&quot;:3008,&quot;referenced_errors&quot;:[{&quot;created&quot;:&quot;@1625178894.878505214&quot;,&quot;description&quot;:&quot;Empty update&quot;,&quot;file&quot;:&quot;src/core/ext/filters/client_channel/lb_policy/pick_first/pick_first.cc&quot;,&quot;file_line&quot;:201,&quot;grpc_status&quot;:14}]}&quot;
  &gt;
  </code></pre>