Requesting overpayment from when I was a teenager

Received a letter from SS 2/8/22 stating I owed $2,534.40 from an overpayment as a child on my mother’s record. This was over 45 years ago. I have no proof and I was given no documentation regarding this. I requested a reconsideration and was just informed it was denied. I am now waiting on a decision on my waiver request.