I have the same problem. I am actually a former tax lawyer. I mailed my 2019 amended return in September, 2020. Then, in February, 2021, I sent them another copy with a cover letter explaining that the enclosed form is a replica of what I mailed in September, 2020.
As far as I can tell, only Drake software supports an amended efiling of a 2019 return, but I am sure there are other providers. I dont agree with the IRS or others that say not to mail it again. I hink that is hogwash, personally.
I am now looking for a professional who will be able to do this for me instead of getting bogged down in purchasing the professional software, like Lacerte or Drake, which require you have an EFIN number (which I do), but it is still a big pain in the neck.
