I am sorry to hear of your issue and can empathize with you - I have a similar problem! The dreaded AGI. I was not able to solve my problem, so can't offer to solve yours, but I like to share my story.
My wife and I have used TT for many years filing as "married joint return". This (2019 tax year) is the first time that our e-file return is rejected, due to supposedly a non-matching AGI for **my wife**. Naturally, I went through all the hoops, double-checked everything, and even obtained a transcript of our 2018 return from IRS to make sure there was no mistaken AGI - I guess I did better than you in that sense. After all, how difficult it is to confirm a number! The bottom line is, the AGI is absolutely correct. Hence, I am at a loss as well.
Having exhausted my energy I have resigned to paper-filing. And there is no need to be pessimistic in your situation either: If your son's (grandson's) SS# is correct, the paper return will be just as good I am sure. What did we do before e-filing, right?
Being a forensic person by training, I started to think if there is a bug or misstep somewhere in the chain - with IRS or TT if not me? The ONLY change for us from 2018 tax year to 2019 tax year is that my wife passed away in March of 2019. We are still eligible to file "married joint return" for 2019 of course (but not 2020) but I figure that may have something to do with my issue this year. In other words, I am inclined to think if my wife's death is not noted on the return, our e-file wouldn't be ejected based on "*my wife's name* AGI is incorrect", i.e., my wife was singled out as the person having an incorrect AGI whereas of course both she and I have the same AGI.
PS: I often wonder why AGI is the only key used for identity purposes (e-signature), not the PIN we were given when e-filing, or SS#, etc.
PPS: Learned a $25 lesson as well. Do not fork out the money for e-filing the state return until I have successfully e-file the federal return. Now that money is wasted.
