Why does a missing parameter error display when I try to add a product to the cart?

Question: Why does a missing parameter error display when I try to add a product to the cart
 
Answer:
When you see an error like the following when trying to add a product to the cart:
ERROR: parameter missing from input Parameter name
This will typically happen during a specific scenario:
 
1.) You're adding a new calculator parameter to your Calculator Pricing Engine
2.) Prior to updating the pricing engine, the product that uses the engine has an item added to the cart
3.) After updating the engine, you try to add the same product again to the cart
4.) The error shows
 
This is due to the first item in the cart using the parameters of the old pricing engine. When the cart is updated with the new item, the original item can't find the new parameters in the details with which it was originally added to the cart.
 
To get rid of the error, remove the old item from the cart and re-add it now that the new pricing engine is active.
 
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