Problems displaying a mesh

Possibilities:

1. world matrix is incorrect.

2. view matrix is incorrect.

3. projection matrix is incorrect.

4. one or more viewport parameters are incorrect.

5. the mesh vertices or indices are incorrect ( winding order incorrect, triangles are degenerate ).

6. the scene viewpoint is inside the cube looking out.

7. you don't set a default texture.

If you can create your own vertex/index buffers correctly to display a cube, load those into ID3DXMesh, and get it to display that way. Then use D3DXSaveMeshToX to save the mesh to an X file. Compare that (successful) file with your unsuccessful file to determine the differences.

have you added a light source ?

// this is the function that sets up the lights and materials
void init_light(void)
{
    D3DLIGHT9 light;    // create the light struct
    D3DMATERIAL9 material;    // create the material struct

    ZeroMemory(&light, sizeof(light));    // clear out the light struct for use
    light.Type = D3DLIGHT_DIRECTIONAL;    // make the light type 'directional light'
    light.Diffuse = D3DXCOLOR(0.5f, 0.5f, 0.5f, 1.0f);    // set the light's color
    light.Direction = D3DXVECTOR3(-1.0f, -0.3f, -1.0f);

    d3ddev->SetLight(0, &light);    // send the light struct properties to light #0
    d3ddev->LightEnable(0, TRUE);    // turn on light #0

    ZeroMemory(&material, sizeof(D3DMATERIAL9));    // clear out the struct for use
    material.Diffuse = D3DXCOLOR(1.0f, 1.0f, 1.0f, 1.0f);    // set diffuse color to white
    material.Ambient = D3DXCOLOR(1.0f, 1.0f, 1.0f, 1.0f);    // set ambient color to white

    d3ddev->SetMaterial(&material);    // set the globably-used material to &material
}
 
//set these after you make the device
 
d3ddev->SetRenderState(D3DRS_LIGHTING, TRUE);    // turn on the 3D lighting
d3ddev->SetRenderState(D3DRS_ZENABLE, TRUE);    // turn on the z-buffer
d3ddev->SetRenderState(D3DRS_AMBIENT, D3DCOLOR_XRGB(50, 50, 50));    // ambient light
 

There are no materials assigned to this mesh, so I'd expect to see a plain white cube.

Or a plain black cube. I hope your background color isn't black ;) That's just a tip, to be sure (maybe you're doing it, but we can never know) - during these initial attempts, never clear your backbuffer to white or black, use some general color, like a yellowish-gray etc :)

Or a plain black cube. I hope your background color isn't black

you will still need lighting regardless if the mesh has no materials or textures