This page needs a browser that runs scripts.
Nothing here is a stored picture — every curve is calculated and drawn as you
use it. In a file previewer that setting is switched off, so the panels come
up empty.
On a computer, open this file in any browser. On a phone, tapping the file in
Mail or Files hands it to the built-in previewer rather than to the browser,
and there is no way to point the browser at a local file; it has to be put on
a web server and opened by address instead.