If you are getting the error message:
"The frame or hanger included in this order is temporarily out of stock. You can choose a different color or product that is in stock to place the order. You can find the latest information about our stock availability in the help center."
it means you are trying to place an order that contains at least an item which is currently out of stock.
Tip: You can find updated information on what items are out of stock here as well as on the product page in the product catalogue. For information about the available options you have when an item is out of stock, we recommend consulting this article.