Issue on sending gRPC request

[SGIRI]

Hello,

i am currently trying to access one of our gRPC service in the proxy. i followed the documentation and used ExternalCallout 

<?xml version="1.0" encoding="UTF-8" standalone="yes"?>
<ExternalCallout continueOnError="false" enabled="true" name="EC-Grpc">
  <DisplayName>EC-Grpc</DisplayName>
  <GrpcConnection>
    <Server name="GRPCService"/>
  </GrpcConnection>
  <TimeoutMs>5000</TimeoutMs>
  <Configurations>
    <Property name="with.request.content">true</Property>
    <Property name="with.request.headers">true</Property>
    <Property name="with.response.content">true</Property>
    <Property name="with.response.headers">true</Property>
  </Configurations>
</ExternalCallout>

`GRPCService` is a target server, where the server of gRPC is added.

when i am trying to call proxy i am getting following error:

{
    "fault": {
        "faultstring": "Encountered the following exception while sending the gRPC request or processing the response: [io.grpc.StatusRuntimeException: INTERNAL: http2 exception].",
        "detail": {
            "errorcode": "steps.externalcallout.ExecutionError"
        }
    }
}

i would be very happy to get some help

Thank you in advanced