cannot be ordered; unavailable for order
Used in commercial contexts to indicate that an item or service cannot be ordered, often due to being out of stock, discontinued, or not offered.
This product cannot be ordered at the moment.
I heard that the dishes marked 'unavailable' on the menu are out of ingredients.
注文可能 means 'can be ordered', the opposite of 注文不可.
売り切れ means 'sold out', a common reason for 注文不可, but 注文不可 can also apply to items never sold or temporarily unavailable.
Compound of 注文 (order) + 不可 (not possible, cannot).