Me and a friend both had this problem. We definetely had an Emblem slot that was clear (I have 3) but when receiving the "Smoldering Flame" Crucible emblem we didn't actually get it. It was only added to collections with no way of reaqcuiring it so this emblem is impossible to actually get.
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Allo there, Smoldering flame is a variant, if you inspect your Fireforged valor emblem, you'll be able to apply the new variant. [url=https://www.bungie.net/en/Help/Article/47568]Emblem variants[/url]