Intersection Observer not working below 600px viewport (+GSAP)

A have problem with my content animation. Everything working fine, but when I make responsive website and make viewport width below 600px, my intersection Observer not working. Nothing happen.

I add console.log to IO and nothing show up in console, when I scroll my website. When I scroll when width is more than 600px, I can see IO in console.

Maybe someone know solution for this problem?

My code:

//global
const slideDuration = 1;

// scroll animation
let target = document.querySelectorAll("section");
const options = {
 root: null,
 threshold: 0,
 rootMargin: "-300px"
};

const contentAnimation = (left, right) => {
  gsap
    .timeline()
    .from(right, { opacity: 0, duration: slideDuration, x: 400 })
    .from(left, { opacity: 0, duration: slideDuration, x: -400 }, "-=0.5");
};

 const io = new IntersectionObserver(entries => {
entries.forEach(entry => {
if (entry.isIntersecting) {
  //show content
  const getElement = entry.target.className;
  const contentElement = document.querySelector(`.${getElement}__content`);
  contentElement.style.opacity = "1";

  //animation
  const right = document.querySelectorAll(`.${entry.target.className}-right`);
  const left = document.querySelectorAll(`.${entry.target.className}-left`);

  contentAnimation(left, right);
  io.unobserve(entry.target);
}
  });
}, options);

target.forEach(section => {
  io.observe(section);
});