OwlCarousel2无法获得视频图像预览

Question

我的视频来自youtube，但视频没有预览图像。

Owl Carousel v2.3.4，jQuery v3.3.1

 $('#owlVideo').owlCarousel({
                    items:1,
                    merge:true,
                    loop:true,
                    margin:10,
                    video:true,
                    lazyLoad: true,
                    nav:true,navText: ["<span aria-label='Previous'  style='font-size:55px'>‹&nbsp;&nbsp;</span>", "<span aria-label='Next' style='font-size:55px'>&nbsp;&nbsp;›</span> "],

                    center:true,
                    responsive:{
                        480:{
                            items:2
                        },
                        600:{
                            items:4
                        }
                    }
                });

    <div class="owl-carousel owl-theme" id="owlVideo">

      <div class="item-video" data-merge="2"><a class="owl-video" href="https://www.youtube.com/watch?v=FBu_jxT1PkA"></a></div>
      <div class="item-video" data-merge="1"><a class="owl-video" href="https://www.youtube.com/watch?v=oy18DJwy5lI"></a></div>
      <div class="item-video" data-merge="2"><a class="owl-video" href="https://www.youtube.com/watch?v=H3jLkJrhHKQ"></a></div>

       </div>

我不明白为什么不能帮忙。