When uploading videos in Micro.blog, the special plug-in “Video streaming” is automatically installed. This plug-in handles enabling support for HTTP Live Streaming in some browsers such as Chrome and Firefox. (Safari already has native support.)
If you’ve edited your theme templates, it’s possible that the hooks for enabling this plug-in could have been overwritten. As a quick fix, you can add the following HTML in your custom footer:
<script src="https://cdn.jsdelivr.net/npm/hls.js"></script>
<script src="/js/studio.js"></script>