Book Cover not appearing after adding it

Hi folks. This is my first post and I'm a Sigil noob. I just self-published my first book last month using Scribus and KDP. I've been working on an epub. I don't remember how I converted the Scribus file to the epub (I should have taken notes on that...) but I do have a good looking epub, so that's not what I'm asking about. My problem is getting the cover to show up!!!

I opened the epub in Scribus and used the work flow shown here:

https://www.youtube.com/watch?v=5gL0jH6pFPg

Yet, when I import the file into Calibre, no cover shows up.

Any ideas?