(for 1.17 servers, I don't know if it will work because I didn't try it yet but you can try if you want. message me if it doesn't)
Note for (Enhanced) shop: You must put an item with the same price in this shop and separate it, because what the buyer selected will be bought with the price you set. So be careful of stacking an item when you refill the shop, you must set what amount will be sold for the price you set. Also, you can put different items in this shop but with the same price, example is for enchanted book with different enchants or spawners with different type.
Note for (Basic) shop: You can only put normal items here, if you wish to sell a custom item or enchanted items, then you choose the enhanced shop instead.