There is a button here that only appears when a certain condition is met. When the URL contains st=Completed we know it is safe to show this button, which will allow a download.
The button below only appears when the URL does NOT contain st=Completed
To understand how this works, you have to look at the Advanced tab for the button, then Dynamic Conditions and Request Parameter Type is GET. Then the Condition field can be something like “is empty” or “Contains” and Compare Type = Text and Conditional Value = “Completed”.