I save lots of web-pages using SingleFile so I always have a copy, but some pages retain a pop-up cookie or other kind of pop-up. You can remove these easily enough from the saved HTML, but sometimes you still can’t scroll.
I insert the below CSS snippet into the saved HTML (anywhere within the <head></head>
tags) and this usually overrides the stupid lack of scrolling.
<style>
body {
overflow: auto !important;
}
</style>