I have the same issue, it appears to be very random. Sometimes they will all show up, other times they wont show up. Sometimes if I leave one page, with all cover images showing, to another page, then return to the first page..the cover images will no longer show. It's very frustrating when I try to show the page to someone and the page looks empty.
I use Google Chrome on PC and Android. Same random behavior regarding invisible cover images. The links all work, and the pictures all show, but the cover images may or may not..most often not.
Cannot speak for the consistency of this over a long period of time as I've just created the page today.
Problem seems to have resolved itself or Adobe is working on this in the background
My site works on PC and iPad
I checked a few sites from other people that were affected as well and they are now working again so you may want to check yours again - hopefully, it is up and running for you also
Yea, I checked and its working for me now. Hopefully this isn't a recurring issue