Labels are not applied to issues created by Utterances

I have integrated Utterances like this:

    <script src="https://utteranc.es/client.js"
            repo="thomaslevesque/blog"
            issue-term="pathname"
            label="post-comment"
            theme="github-light"
            crossorigin="anonymous"
            async>
    </script>

It works fine, except that the post-comment label is not applied to issues. It worked the first time I tried it (see this issue -- there isn't actually a comment because I deleted it), but since then Utterances never applied the label.

Note: the only time it worked, I was the one commenting. Could this be because I'm the repo owner?