If you are sure that you never got a letter about the maltreatment determination, get a copy of your child or adult protection file. You get this from the county where the maltreatment determination was made. See if a letter from the state or county is in it. If not, ask the state or county agency to give you a chance to fight the accusation (appeal).
First, you have to appeal the letter telling you that you are disqualified from working at a certain job. Appeal in writing before the deadline stated in the letter.
Next, tell the hearing officer and the opposing lawyer you want to reopen the maltreatment determination. Tell them you did not get notice of the maltreatment accusation when it was made against you.
If you are stuck with a maltreatment record, remember after 7 to 10 years the maltreatment does not affect caretaker jobs and you can try to work in those jobs again. Also, a maltreatment record does not stop you from working in any other jobs that do not require direct contact with vulnerable adults or children.