I had to re-download and reinstall Studio after needing to wipe my hard disk clean and reinstall Windows. I originally purchased the 2019 version, but the download gave me 2021. When I purchased the 2019 version and activated it in July 2020, I did not upgrade when the 2021 version became available because I was too busy. Now I would like to either activate 2021 version I have installed, or revert to the 2019 version I purchased. When I try to activate the installed version, using the number that is listed for the product I purchased. I get this error:  "Activation Key. Invalid Product Key. Make sure the Product Key belongs to the intended product or product version."