using protobuf reflection to get a boolean field descriptor in c++

I am using grpc in a C++ application. On the client side, I need to reflectively query a boolean value from a message using reflection.

The response message is shown below. Unfortunately I cannot see field descriptors for the bool mAP field - I can however see the FieldDescriptors for the string fields, What am I doing wrong?

John

message Response {
    // OTP Connection Status
    enum OTPConnStatus {
        Disconnected              = 0;
        Connected                 = 1;
        InvalidCS                 = 2;
        DiscRequest               = 3;
    }

    // define the fields
    RXMessageType mMessageType    = 1;
    bool mAP                      = 2;
    OTPConnStatus mCS1            = 3;
    OTPConnStatus mCS2            = 4;
    OTPConnStatus mCS3            = 5;
    OTPConnStatus mCS4            = 6;
    string mOTP1                  = 7;
    string mOTP2                  = 8;
    string mOTP3                  = 9;
    string mOTP4                  = 10;
}

const auto reflection = pMessage->GetReflection();
std::vector<const FieldDescriptor*> fields;
pMessage->GetReflection()->ListFields(*pMessage, &fields);
const auto fieldIter = std::find_if(fields.cbegin(), fields.cend(),
    [&lcFieldName](const FieldDescriptor* next) {
        return boost::iequals(next->name(), lcFieldName);
    });
if (fieldIter != fields.cend()) {
    std::string result;
    auto fieldDescriptor = *fieldIter;
    if (!fieldDescriptor->is_repeated()) {
        switch (fieldDescriptor->cpp_type()) {
        case FieldDescriptor::CPPTYPE_INT32:
            result = std::to_string(reflection->GetInt32 (
                *pMessage, fieldDescriptor));
            break;
        case FieldDescriptor::CPPTYPE_INT64:
            result = std::to_string(reflection->GetInt64 (
                *pMessage, fieldDescriptor));
            break;
        case FieldDescriptor::CPPTYPE_UINT32:
            result = std::to_string(reflection->GetUInt32 (
                *pMessage, fieldDescriptor));
            break;
        case FieldDescriptor::CPPTYPE_UINT64:
            result = std::to_string(reflection->GetUInt64 (
                *pMessage, fieldDescriptor));
            break;
        case FieldDescriptor::CPPTYPE_DOUBLE:
            result = std::to_string(reflection->GetDouble (
                *pMessage, fieldDescriptor));
            break;
        case FieldDescriptor::CPPTYPE_FLOAT:
            result = std::to_string(reflection->GetFloat (
                *pMessage, fieldDescriptor));
            break;
        case FieldDescriptor::CPPTYPE_BOOL:
            result = reflection->GetBool(
                *pMessage, fieldDescriptor) ?
                "true" : "false";
            break;
        case FieldDescriptor::CPPTYPE_ENUM:
            result = reflection->GetEnum(
                *pMessage, fieldDescriptor)->
                    full_name();
            break;
        case FieldDescriptor::CPPTYPE_STRING:
            result = reflection->GetString(
                *pMessage, fieldDescriptor);
            break;
        case FieldDescriptor::CPPTYPE_MESSAGE:
            //result = reflection->GetMessage(
            //    *pMessage, fieldDescriptor);
            break;
        }
    }
    std::cout << result << std::endl;
    exit(0);
} else {