@Zean, did you upgrade your store to v1.5.5 or do an install of 1.5.5? A template "qualifies" for display if it's, as you found, got entries in the layout_boxes table and it's not the template_default (you'd clone classic instead) template.

My guess is that you upgraded from an earlier version of Zen Cart, since the ZC 1.5.5 upgrade SQL, for some reason, doesn't set the layout_boxes configuration for the responsive_classic into the database.