Bootstrap 4 为什么这些嵌套的引导行不起作用

我在一个引导列中有两级嵌套的引导行。我已经在代码中注释了哪些有效，哪些无效。如果我希望嵌套行中的每一列仅为6，则它将显示为6，但下一列不会填充其他6，而是将其包裹在下面。在每种情况下，都不会显示两列。很难描述引导问题，而且该网站尚未发布，所以我无法展示

<div class="container-fluid">
    <div class="row">
        <div class="col-12 col-lg-9"> <!--this works-->
            <div class="iframe-container">
                <iframe src="https://player.vimeo.com/video/23912696" allow="autoplay; fullscreen" allowfullscreen></iframe>
            </div>
        </div>
        <div class="col-12 col-lg-3"> <!--this works-->
            <row>
                <div class="col-6 col-lg-12"> <!--this doesn't work-->
                    <row>
                        <div class="col-6"><img src="images/plasticSurgery.jpg" class="thumb" /></div><!--this doesn't work-->
                        <div class="col-6 thumbP">Plastic Surgery</div><!--this doesn't work-->
                        <div class="col-6"><img src="images/plasticSurgery.jpg" class="thumb" /></div><!--this doesn't work-->
                        <div class="col-6 thumbP">Plastic Surgery Dr</div><!--this doesn't work-->
                    </row>
                </div>
                <div class="col-6 col-lg-12"> <!--this doesn't work-->
                    <row>
                        <div class="col-6"><img src="images/plasticSurgery.jpg" class="thumb" /></div> <!--this doesn't work-->
                        <div class="col-6 thumbP">Plastic Surgery</div> <!--this doesn't work-->
                        <div class="col-6"><img src="images/plasticSurgery.jpg" class="thumb" /></div> <!--this doesn't work-->
                        <div class="col-6 thumbP">Plastic Surgery</div> <!--this doesn't work-->
                    </row>
                </div>
            </row>
        </div>
    </div>
</div>

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整形外科医生
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整形外科

不是有效的HTML元素。也许你应该用以下方法来改变它：

<div class="row"></div>

---

这是定义行容器的自举方法。

是的，我在外行上有正确的定义，但在内行上没有。该死的打字错误。我看代码看得太久了。谢谢

<div class="row"></div>