I just tried to do this & was informed by support that they can only supply customers with TurboTax products for the 3 prior tax years. Thus, as of 2020, if you need to amend a return for a year prior to 2017, you have to go out in the market and find a desktop version of the product and purchase it.
Shame on you, Intuit. Very, very poor customer support!! I am very disappointed today.
