I recently discovered I made a mistake on my 2021 return that I need to amend. Upon logging into Turbo Tax online, I don't see the 2021 return in my documents. I am pretty sure it's because I used the desktop version of TT that year to file. I have a new computer now and don't have the CD or desktop version of TT anymore. I do have a copy of my return along with the actual file of my original return (.lnk file), but I can't open it. How can I go about amending this return?