Niagara System doesn't use render target texture that produced by another render target?

My niagara vfx need a sample texture to work and this texture was create by:
First, a scene capture 2d draw onto a render target A texture.
Then use a material which have a blur node to blur the render target A texture and using blueprint to generate another render target B 20 times per second.
Finally I want my niagara to sample this render target B texture.

But the niagara couldn’t sample the render target B texture. I can see the texture A and B are created and updated 20 times per second in scene(create a material using the texture and put it onto a plane) and the niagara work when sample render target A texture. Why it doesn’t work when generate the render target B texture?

(I also observed that when I preview the render targets window while playing, the render target A are updated but not B)
Ver: 4.26.2