Godot C++ NativeScript version not rendering multimesh instance whereas GDScript version does

I am new to Godot. I am aiming to create a RTS game with 10’s of thousands of units and for it to run smoothly. So I’m looking to use GDNative C++ with the Visual Server to handle updating and moving the units and GDScript for everything else.

The following script in GDScript successfully renders a single multi mesh cube at the center of the screen.

extends Spatial

func _ready():

    var meshRid=preload('res://new_cubemesh.tres').get_rid()
    var multimesh = VisualServer.multimesh_create()

    VisualServer.multimesh_allocate(multimesh, 1, VisualServer.MULTIMESH_TRANSFORM_3D, 
    VisualServer.MULTIMESH_COLOR_NONE, VisualServer.MULTIMESH_CUSTOM_DATA_FLOAT)
    VisualServer.multimesh_set_mesh(multimesh, meshRid)

    var instance = VisualServer.instance_create()
    var scenario = get_world().scenario

    VisualServer.instance_set_scenario(instance, scenario)
    VisualServer.instance_set_base(instance, multimesh)

I have implemented the alternative In GDNative (C++) and while it doesn’t crash and does run the code, it does not render the cube. Camera is in correct position to observe the cube at 0,0. I’ve just re-purposed the GDNative C++ tutorial for now.

I really like the community here and the engine so far, so hopefully I am just misunderstanding something here and it is possible what I am trying to achieve.

Thank you for your time, c++ scripts below.

gdexample.cpp

#include "gdexample.h"

using namespace godot;

void GDExample::_register_methods() {
    register_method("_process", &GDExample::_process);
    register_method("_ready", &GDExample::_ready);
}

GDExample::GDExample() {
}

GDExample::~GDExample() {
    // add your cleanup here
}

void GDExample::_init() {
    // initialize any variables here
    base=5;
}

void GDExample::_ready(){

    visual = VisualServer::get_singleton();
    loader = ResourceLoader::get_singleton();

    Ref<Resource> meshResource = loader->load("res://new_cubemesh.tres");
    RID meshRid = meshResource->get_rid();

    multimesh = visual->multimesh_create();
    visual->multimesh_allocate(multimesh, 1, visual->MULTIMESH_TRANSFORM_3D, visual->MULTIMESH_COLOR_NONE, visual->MULTIMESH_CUSTOM_DATA_FLOAT);
    visual->multimesh_set_mesh(multimesh, meshRid);

    RID instance = visual->instance_create();

    Ref<World> world = get_world();
    RID scenario = world->get_scenario();
        
    visual->instance_set_scenario(instance, scenario);
    visual->instance_set_base(instance, multimesh);

}

void GDExample::_process(float delta) {
    return;
}

Let me know if you need gdexample.h or gdlibrary.cpp and I can add, the formatting gets messed up if I include them here for some reason. It’s basically just the tutorial stuff though.