swiper doesn't work on page load

Question

I imported the code from https://github.com/nolimits4web/Swiper/blob/master/demos/23-thumbs-gallery.html

But the first problem I had was that the slider didn't show so I fixed that with adding min-height: 250px; to the div class .swiper-slide(this is the only thing I changed), my new problem is that the slider doesn't work.
When I resize the browser the slider suddenly works, I can't find what is causing the problem.

You can watch the slider at nielsvt.remvoo.com and then section portfolio, the slider will be visible at the bottom of the page

Answer 1

I had a similar issue. I simply fixed it by initializing the swiper once the page loads.

useEffect(()=> {
    swiper.init()
}, [])

Answer 2

On the swiper section definition put the observer property true.

const swiper = new Swiper(swiperIdentifier, {
      ...
      observer: true,
    });