Setting the AGI 0 is 1::1 equivalent to saying "I didn't file last year" in the interview step, BTW.
More accurate would be the statement, "I didn't file, or the IRS did not process my return early enough to enter my AGI into the verification database". In our case, a mid-June filing was not acted upon until late November and not resolved until mid December 2020. Lots of this in the year of COVID, I imagine.
Remember if you are going to try this for a joint return that you need to set AGI to 0 for both parties aka replying "We both didn't file last year". I forgot this and having fixed my AGI to zero, got a second reject citing the spousal PIN and AGI as not matching rather than the original one citing my information. Editing the information to say "we both did not file" when preparing to file set both AGI fields to zero, I submitted again and then (finally) the return was accepted.
Hoping this helps someone else.
