Epic marketplace copyright issue

I have submitted a material pack recently
and it has a starter content texture in it for demonstration
but Epic recently send me the result saying changes needed
they say that the image I am using is copyrighted
and someone is selling it.
The fire texture is shown in the attached image. It is the one that I am using
The file name is T_Fire_Tiled_D
what steps should I be taking?
I told Epic that I am using the Starter content textures
but they said that I am using copyrighted content that is created by some third party