I had the exact same experience, except both the 2022 and 2021 amendments for state were provided as a paper return with instructions.
Turbo Tax submitted both federal amendments for 2022 and 2021 by efile. Federal 2022 was accepted and Federal 2021 was rejected instantly with no error code.
So if it's really true that federal returns for prior years need to be submitted on paper, where's the matching instruction sheet from the software? Why did it try to submit it?
