Not sure I am understanding, let me recap your situation, 

You filed parents 2019 return marking box they were being claimed on another return. They had no taxable income, so no refund, and they were accepted.

You filed Daughters 2019 return claiming parents as dependents, and her return was rejected code IND-512-01.

If this is what happened, you will not be able to efile parents return again as they have already been accepted.

You will have to mail in daughters return, because you cannot resolve the error.

You said you filed parents return last year meaning 2018. if you did not file parents 2019 return, then I believe the parents are a victim of ID theft

Just to be sure I would recheck very carefully everyone's SS numbers, and if they are correct I don't believe you will be able to efile daughter's return