Only 2019 and 2020 can Efile federal amended returns.   For 2019 YOU need to have Efield the federal return using ProSeries.   For 2020, they show the option for Efiling an amended return even if you didnt Efile the original, but Ive seen mixed results with this, many people still cant get it to go through.

https://proconnect.intuit.com/community/amend-tax-return/help/how-do-i-amend-an-individual-return-us...