I reread your original post again.
Did you file a full tax return yourself in 2019?
if yes, then why did you file at the non-filer website?
if no, then you've already claimed this child on the non-filer form which is why your father can not claim the child.
am I missing something?
normally, only one person can claim a child. Who is providing more than 50% of the child's support. typically that is a critical factor in determining who CAN claim the child.
