I am having the same issue. I went and changed which statistic is shown on one tile and that single one now shows up. it could be how you have the layer configured for public use/viewing.
EDIT: I went back and found out the layer it is referencing was set to admin only, and it cant be shared globally due to it being editable.
if you want it be viewable by the general public, go back and make a viewing feature service layer from the feature layer and share that to public without any editing capabilities.
Then go back into your cards, select that new layer and redo your statistics. It should show up then on the site without needing a login.
