Looks like the nicest RSS Reader in existance BUT: Not working in Firefox Developer Edition Version 60.0b4 46-bit

Can't see any contents on the big right side area (it states "no items") and on the left hand menu there are items that I can open up (under the feed name), but they do not have any title/text. So I do recognize that there are items as I have the arrows I can click at that show that they contain content, but there's just no text there.

I tried adding:
https://www.sellxed.com/shop/de/chf/software/rss/index/prestashop-powerpay-zahlungs-modul.html