CubeTexture from CubeRenderTarget not working in fragment shader

Hi there, I’m trying to use the CubeTexture generated from CubeCamera in a fragment shader with textureCube() function. But I got black screen. When I load a CubeMap with local texture image, the fragment shader works well. The CubeTexture also works great with MeshStandardMaterial. My abstract version of code and issue can be seen here When it’s working, the object should be blue. Can someone point me the problem in my code please?