After my wife brought home a store-baked Roscón de reyes, I decided to make one, myself, only using sourdough. I used a formula from David Jorge's food show that featured Iban Yarza. Wary that I'd under-proof it, I gave it extra time to bulk ferment it. The results were amazing. Enriched doughs, especially with sourdough, need more time to ferment from all the additions (e.g. sugar, spices, butter, etc.)  All to say, patience is key so… wait for it.