Hdr effect on Model vanishes in Ar.js + Three.js

Questions
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1

Hi
I was trying to add hdr reflection on my model in Ar.js + threeJS.
The first time, the model renders the hdr effect is visible but after something hdr effects vanish. Or If I refresh the page, the hdr effect vanishes. I using the following code to add an hdr effect.

const pmremGenerator = new PMREMGenerator(renderer);
pmremGenerator.compileEquirectangularShader();
const rgbeLoader = new RGBELoader();
rgbeLoader.setDataType(UnsignedByteType).load(background, (texture) => {
  const envMap = pmremGenerator.fromEquirectangular(texture).texture;
  scene.environment = envMap;
  texture.dispose();
  pmremGenerator.dispose();
  render();
});

Plz suggest me a solution?