Yes I am - actually all my posts do have featured images already. I've tried to add new posts with featured images as I assumed it's maybe not working for old content but that did not change anything.
My settings in Style Properties for XPress are:
- Article List Layout style: List
- Article thumbnail size (for list style only): Medium
I've attached a screenshot of one article in Wordpress (it's the most recent version 4.9.8).
The featured image also does show up in the header of the article as well as on Wordpress as a featured post, just not in the list.
As mentioned, I'm only using the Xpress addon and UI.X.