you cannot e-file those years. it is too late to claim a refund for 2020 that had to be file by 5/17/2024. it is too late to claim a refund for 2021 unless it was properly extended. without a proper extension the deadline to claim a refund was 4/15/2025. with a proper extension the deadline is 10/15/2025. if you owe there is no deadline, but Turbotax no longer supports 2020. for 2021 you would need the desktop app since online preparation is closed
https://turbotax.intuit.com/personal-taxes/past-years-products/2021/
