Well if you qualified inthe last three years, it’s my understanding you can do 1040X’s and reap your just rewards. But I’m nothing more than an average Joe with two eyeballs and two thumbs when it comes to taxes.
EDIT: According to this, you can file 1040-X’s electronically only for the last three years. I haven’t found any limitation or not beyond that. You could ask at the library. They usually have people helping with taxes voluntarily there.
I have no idea how long this EITC has been available.
Maybe @stollcpa can weigh in here. I find it hard to believe that all these years TaxAct hasn't accounted for this. I get how I would be eligible now with my income being so low (not counting Social Security).