Been potty training my daughter since she was two years old, she's now four &will sit on the potty, do nothing,is she being stubborn or something else?

Adaptive/Self-Help: Delays require medical, neurological & developmental assessment. Medical causes may require referral to a specialist. Behavioral causes from parents' accidentally having reinforced toileting refusal may require referral to a child psychologist & a pediatric GI to manage stool-withholding & constipation wth techniques like those in comments, if health is fine & development is otherwise typical.