Category Order could not understand your category HTML. Please do the following:

• Disable all plugins except for category order to see if some other plugin is causing the problem. If the problem goes away, re-enable each plugin until you find the incompatible one.
• Try switching to a different theme, like the WordPress default theme.

Once you have tried the above steps, email david@coppit.org with the results of these debugging steps. Also include the following information:

Original HTML:
<li class="cat-item cat-item-1"><a href="https://www.yamechuouhoikuen.com/category/info/">お知らせ</a>
</li>
<li class="cat-item cat-item-9"><a href="https://www.yamechuouhoikuen.com/category/violet/">すみれ組</a>
</li>
<li class="cat-item cat-item-10"><a href="https://www.yamechuouhoikuen.com/category/dandelion/">たんぽぽ組</a>
</li>
<li class="cat-item cat-item-7"><a href="https://www.yamechuouhoikuen.com/category/flowerbud/">つぼみ組</a>
</li>
<li class="cat-item cat-item-11"><a href="https://www.yamechuouhoikuen.com/category/sunflower/">ひまわり組</a>
</li>
<li class="cat-item cat-item-8"><a href="https://www.yamechuouhoikuen.com/category/peach/">もも組</a>
</li>
<li class="cat-item cat-item-12"><a href="https://www.yamechuouhoikuen.com/category/lily/">ゆり組</a>
</li>
<li class="cat-item cat-item-4"><a href="https://www.yamechuouhoikuen.com/category/event/">行事</a>
</li>

Processed HTML:
<li class="cat-item cat-item-1"><a href="https://www.yamechuouhoikuen.com/category/info/">お知らせ</a>
</li>
<li class="cat-item cat-item-9"><a href="https://www.yamechuouhoikuen.com/category/violet/">すみれ組</a>
</li>
<li class="cat-item cat-item-10"><a href="https://www.yamechuouhoikuen.com/category/dandelion/">たんぽぽ組</a>
</li>
<li class="cat-item cat-item-7"><a href="https://www.yamechuouhoikuen.com/category/flowerbud/">つぼみ組</a>
</li>
<li class="cat-item cat-item-11"><a href="https://www.yamechuouhoikuen.com/category/sunflower/">ひまわり組</a>
</li>
<li class="cat-item cat-item-8"><a href="https://www.yamechuouhoikuen.com/category/peach/">もも組</a>
</li>
<li class="cat-item cat-item-12"><a href="https://www.yamechuouhoikuen.com/category/lily/">ゆり組</a>
</li>
<li class="cat-item cat-item-4"><a href="https://www.yamechuouhoikuen.com/category/event/">行事</a>
</li>

Category pattern:
/http\:\/\/www\.yamechuouhoikuen\.com.*?\/category\/(?:[^\/"]+\/)*([^\/"]+)/

Items:
Array
(
    [0] => <li class="cat-item cat-item-1"><a href="https://www.yamechuouhoikuen.com/category/info/">お知らせ</a> </li>
    [1] => <li class="cat-item cat-item-9"><a href="https://www.yamechuouhoikuen.com/category/violet/">すみれ組</a> </li>
    [2] => <li class="cat-item cat-item-10"><a href="https://www.yamechuouhoikuen.com/category/dandelion/">たんぽぽ組</a> </li>
    [3] => <li class="cat-item cat-item-7"><a href="https://www.yamechuouhoikuen.com/category/flowerbud/">つぼみ組</a> </li>
    [4] => <li class="cat-item cat-item-11"><a href="https://www.yamechuouhoikuen.com/category/sunflower/">ひまわり組</a> </li>
    [5] => <li class="cat-item cat-item-8"><a href="https://www.yamechuouhoikuen.com/category/peach/">もも組</a> </li>
    [6] => <li class="cat-item cat-item-12"><a href="https://www.yamechuouhoikuen.com/category/lily/">ゆり組</a> </li>
    [7] => <li class="cat-item cat-item-4"><a href="https://www.yamechuouhoikuen.com/category/event/">行事</a> </li>
)