Thank you again for your assistance, it is greatly appreciated.
I went to https://www.stardock.com/support/product-key-retrieval but received the following message:
When I did the lookup, I used the same email address to which my receipt and product code were originally sent to me back in 2019.
The Groupy purchase IS showing in my Stardock account (which is also under the same email address I used when I made my original purchase) on the Order History page, but it is NOT showing on the My Downloads page. It's like it isn't associated with my account, even though I have the purchase receipt showing the email address which was used to make the purchase.