Hi Dan, thanks a lot for the feedback!
I ended up noticing that in other Themes (such as the default Atom theme) this error I reported above was not happening, so I interpreted it as being a configuration problem in the platform. I checked the group options and in the "anonymous" group I enabled the "read" option for the Master. This ended up showing the image in the "popular this week" even though I was logged out of the admin option. However, the display of the thumbnails in anonymous mode are still disabled (and in administrator mode displaying normally), but even though I changed all the read and view options in the anonymous group I still could not display the thumbnail.
now making a reference to the github README where Alberto published his theme, it is written the following: "By default, Atom permissions allow descriptions to be read in browse lists, sidebar facets, "Popular this week" list. This theme removes any items that a specific user, or user group, doesn't have permissions to read;"
I think this information may be the key to the situation, but I don't know exactly how to proceed