Can't setup collapce for spoiler in Bootstrap 4?

Question

Layout

I can't set up collapce for a spoiler in Bootstrap 4. I tried to do everything as in the documentation. But
hobotrobots.devshift.co.uk at the very bottom refuses to work correctly. When you press the button, it appears and immediately disappears.

Answer 1

Remove from here:
description d-flex justify-content-between flex-column collapse show
This is:
d-flex