The amended return I am attempting to e-file today, April 2023, is for the 2021 and it is a VERY SIMPLE tax return for my college-aged kidult. I can't imagine what complexity it has in it that "might" make it not eligible.
To restate previous notes, the software says the amended return is eligible to be e-filed. Yet is fails due to a [false] validation being enforced by the software that the signature date must be inside the calendar year of the ORIGINAL filing. It should instead be validating that the signature is within THREE years of the filing date of the original return (with extensions factored in).
