i downloaded it but it wasn't in html format.
how do i download it in html format?
...That's the file type filter for the "save file" dialog. It simply means you can see all existing files when choosing a name for your export.
...I just tried it, and Twine offered to publish my game in a file with the same name as the story and the .html extension. You only had to press OK. Please double-check what you did.