Do this now: press Cmd+U. The heading, the price and the button are all there in the raw HTML. Crawlers, link previews and slow phones all get real content immediately.

Then do this: reload and smash the Enroll button instantly. For the first 3 seconds it does nothing. It looks ready. It is not. That gap is called hydration, and it is the single most common "the page is broken" complaint that is not actually a bug.