Need to amend 2017 return, but online account won't let me access my return.

I need to amend my 2017 return by 2/1/21.  I paid for the online software on 2/1/18, but when I go to amend that year it gives me these instructions:

How to amend your 2017 return

1. Download your .tax file
2. Then download TurboTax Desktop 2017  for Windows or for Mac
3. Finally, open your .tax file using TurboTax Desktop 2017, and amend your return. 

If I used my online account, why won't it let me amend that year?  Is it because it was 3 years ago?  I can amend 2018 if I needed to.