What’s wrong with my wallpaper liner?

I’m using 1400 grade wallpaper liner, but after applying it, I can still see the texture of the wall when viewed from a side light. It’s not as smooth as I expected. Is there a way to fix this before wallpapering over it?

I’m using 1400 grade wallpaper liner, but after applying it, I can still see the texture of the wall when viewed from a side light. It’s not as smooth as I expected. Is there a way to fix this before wallpapering over it?