Thanks! But I figured it out. ![smiley smiley](https://twinery.org/questions/qa-plugin/wysiwyg-editor/ckeditor/plugins/smiley/images/regular_smile.png)
What I thought was a link – on my Patreon page – to the compiled HTML file, was actually a link to an attached file. No wonder it didn't work!
The solution was to upload the compiled HTML file to a different web page, and link to that. Thanks for helping me, Exile, even though in the end I was just being a dumbass.