If it's a joint return, be sure you are using the same total AGI for both spouses. Do not divide it.
Be sure it's the AGI from the original 2017 return, not an amended one.
If the return was filed real late, such as November 2018 or later, try an AGI of 0.
In any case, before giving up and printing and mailing, try an AGI of 0. Sometimes it works with no good explanation. Kind of like a "Hail Mary" football pass.
