I am also having the same issue. Please note that the post makes a reference to a new popup that appears when you click on + New then Refund. The message states 

----"Keep your payments and refunds organized

If this payment is related to an existing invoice or sales receipt, select the invoice or sales receipt from All Sales and process your refund there"---

but there is no different OR new way to issue the refund, as the popup suggests. 

What is the answer? Is it that there is a new feature coming that is just not available yet? Why have the popup for something that you cannot action?