Posts still not displaying full width

Site: https://futuregenlabs.com/

A couple of months ago, you provided instructions for getting my posts to display at the full column width of 480px (450 + 15 + 15px).

I followed your instructions, but the magic hasn’t worked this time, and an empty sidebar is still showing to the right of a narrow content area.

See test post here: https://futuregenlabs.com/test-post-link/

I’d be grateful if you’d look at the settings below, to see if I’ve made an error or missed out a step.

Thanks for your help.

BLOG PAGE (TEMPLATE)
https://futuregenlabs.com/blog
Template: Blog

CUSTOM CSS
@media (min-width:900px) {
.postlist article {
width: 480px;
}
}

READING SETTINGS
Front page displays
Posts page: Select