All Upfront themes appear to have a bug on a multi-site arrangement, or at least within my install, whereby they 'appear' to work fine, but when you come to edit the theme at the front end using the customizer, it just sits there and loads.
By my investigation, it appears to be looking at the root domain for instruction, and not the sub-folder blog in Console view, but it also has added an options table in the root SQL database, and not one for the sub-folder blog. Thus is sits, and loads and loads, and loads, but no editing. I have repeated this same problem with a new setup, basic multi-site with multi-domains and pro-sites plugin, and apply upfront theme to registered blog, and loading, loading, loading. Love the concept, love the themes. Any suggestions on a possible work-around welcomed.