A plane can't refraction the mesh behind it

[fanbinnet]

A plane can't refraction the mesh behind it.
Please tell me what I am doing wrong, any advice is greatly appreciated.

The material file：
name : ThinRefraction,
shadingModel : lit,
refractionType : thin,
refractionMode : screenspace,
specularAntiAliasing : true,

    material.baseColor.rgb = float3(1.0,1.0,1.0);
    material.baseColor.a = 1.0;
    material.roughness = materialParams.roughness;
    material.ior = materialParams.ior;
    material.transmission = materialParams.transmission;
    material.metallic = materialParams.metallic;
    material.sheenColor = materialParams.sheenColor;
    material.sheenRoughness = materialParams.sheenRoughness;
    material.clearCoat = materialParams.clearCoat;
    material.clearCoatRoughness = materialParams.clearCoatRoughness;
    //material.anisotropy = materialParams.anisotropy;
    material.microThickness = materialParams.thickness;
    material.reflectance = 0.01;

    glassInstance.setParameter("baseColor", 1.0f, 1.0f, 1.0f)
    glassInstance.setParameter("roughness", 0.2f)
    glassInstance.setParameter("transmission", 1.0f)
    glassInstance.setParameter("ior", 1.5f)

But I find the doc can do these like below:

[romainguy]

Make sure the other mesh isn't transparent.

[fanbinnet]

The other mesh inn't transparent.
You can see the bottom of the shader ball mesh.

[fanbinnet]

Thanks for the sugesstion.
I write wrong blend mode for material file.