Problems with dragonfly

Hello, I need help. I was doing quests just to get more reputation with Sabellian because I want to buy a customization piece for my dragon. The problem comes when I want to buy that item. I have enough reputation to get it, but when I try to buy it, nothing happens. Please help me.

What item are you trying to purchase?

You can try a UI reset to start, a corrupted UI can block buying. Follow all the steps in the below article. It will reset all your settings and such in game.
If it doesn’t help, you can revert everything back afterwards if you rename/move the three folders back.

Edit: You do also have the right items in your inventory to purchase the item, right? Most items sold by vendors in DF need crafting reagents, and it has to also be the quality indicated on the tooltip. Can’t use a 3 star Draconium Ore if it calls for a 2 star.