UA_Client_Service_read only yields empty responses
You need to set nodesToReadSize:
    UA_ReadRequest request;
    UA_ReadRequest_init(&request);
    UA_ReadValueId ids[nodeCount];
    
    for (int i = 0; i < nodeCount; i++)
    {
        UA_ReadValueId_init(&ids[i]);
        ids[i].attributeId = UA_ATTRIBUTEID_VALUE;
        ids[i].nodeId = nodesToRead[i];
    }
    request.nodesToReadSize = nodeCount;
    request.nodesToRead = ids;


I am trying to create a small program in C which will poll a frame of data over a opc/ua connection using the open62541 library and the forward it to a kafka server.
Everything works fine when fetching the values from the nodes separately but I would like to use a UA_ReadRequest for that. The problem is that I am only receiving empty responses.
The opc/ua server is coded with in python using the freeopc package.
This is the function that tries tu use a UA_ReadResponse to fetch a several values for specified nodeIDs:
void retrieveOPCData(void)
{
    UA_ReadRequest request;
    UA_ReadRequest_init(&request);
    UA_ReadValueId ids[nodeCount];
    
    for (int i = 0; i < nodeCount; i++)
    {
        UA_ReadValueId_init(&ids[i]);
        ids[i].attributeId = UA_ATTRIBUTEID_VALUE;
        ids[i].nodeId = nodesToRead[i];
    }

    request.nodesToRead = ids;

    for (int i = 0; i < nodeCount; i++)
    {
        UA_LOG_INFO(UA_Log_Stdout, UA_LOGCATEGORY_USERLAND, "ID%i: %s, %i", i,
            request.nodesToRead[i].nodeId.identifier.string.data,
            request.nodesToRead[i].nodeId.namespaceIndex);
    }

    UA_ReadResponse response = UA_Client_Service_read(client, request);

    UA_LOG_INFO(UA_Log_Stdout, UA_LOGCATEGORY_USERLAND, "Status: %i",
        response.responseHeader.serviceResult);
    UA_LOG_INFO(UA_Log_Stdout, UA_LOGCATEGORY_USERLAND, "Responses: %li", response.resultsSize);
}

The result value is UA_STATUSCODE_GOOD but the number of responses is 0. It works fine when fetching the values one after the other like this:
void readNodeAtIndex(int index)
{
    if (index >= nodeCount)
    {
        UA_LOG_INFO(UA_Log_Stdout, UA_LOGCATEGORY_USERLAND, "Index out of Range");
        return;
    }

    UA_Variant variant;
    UA_Variant_init(&variant);

    const UA_NodeId nodeId = nodesToRead[index];

    UA_StatusCode retval = UA_Client_readValueAttribute(client, nodeId, &variant);

    if (retval == UA_STATUSCODE_GOOD && UA_Variant_hasScalarType(&variant,
        &UA_TYPES[UA_TYPES_DOUBLE]))
    {
        UA_Double value = *(UA_Double*)variant.data;

        UA_LOG_INFO(UA_Log_Stdout, UA_LOGCATEGORY_USERLAND, "Double-Value: %f", value);
    }
    else if (retval == UA_STATUSCODE_GOOD && UA_Variant_hasScalarType(&variant,
        &UA_TYPES[UA_TYPES_BOOLEAN]))
    {
        UA_Boolean value = *(UA_Boolean*)variant.data;

        UA_LOG_INFO(UA_Log_Stdout, UA_LOGCATEGORY_USERLAND, "Boolean-Value: %i", value);
    }
    

    UA_Variant_clear(&variant);
}

The opc/ua server is setup like this:
server = Server()
space_url = "opc.tcp://localhost:61032"
server.set_endpoint(space_url)
server.set_security_policy([ua.SecurityPolicyType.NoSecurity])
node = server.get_objects_node()

