C++ Directx 11 Ambient Lighting

I'm currently having a problem with lighting in Directx 11, actually its ambient lighting. Here is the code:

 cbuffer ConstantBuffer
{
    float4x4 final;
    float4x4 rotation;    // the rotation matrix
    float4 lightvec;      // the light's vector
    float4 lightcol;      // the light's color
    float4 ambientcol;    // the ambient light's color
}

struct VOut
{
    float4 color : COLOR;
    float4 position : SV_POSITION;
};

VOut VShader(float4 position : POSITION, float4 normal : NORMAL)
{
    VOut output;

    output.position = mul(final, position);

    // set the ambient light
    output.color = ambientcol;

    // calculate the diffuse light and add it to the ambient light
    float4 norm = normalize(mul(rotation, normal));
    float diffusebrightness = saturate(dot(norm, lightvec));
    output.color += lightcol * diffusebrightness;

    return output;
}

float4 PShader(float4 color : COLOR) : SV_TARGET
{
    return color;
}

Then i send the values to the shader:

ambLight.LightVector = D3DXVECTOR4(1.0f, 1.0f, 1.0f, 0.0f);
ambLight.LightColor = D3DXCOLOR(0.5f, 0.5f, 0.5f, 1.0f);
ambLight.AmbientColor = D3DXCOLOR(0.2f, 0.2f, 0.2f, 1.0f);

ShaderManager.UpdateSubresourceDiffuseShader(devcon);

And then i get the following:

Why?

I tried your shader and seems to work, so maybe some variable are not passed correctly.

you could try to directly set one variable name to color output:

output.color = lightvec;

and

output.color = lightcol;

As a start, so you could double check values are passed properly.