Reinstall Reckon Personal on a new computer


I have been using Reckon Accounts personal Plus 2015 on an old laptop. It is licensed until May 2022. How can install it on my new computer. I downloaded 2020 but it won't accept my product key. The site does not seem to give me the ability to download 2015 - only real old ones like 2006 or 2020 or 2021.