FMLA and termination for failing to submit certification

Q. Our company has an employee who has taken FMLA leave to care for his sick child. His attendance record has been poor, but we have not documented our warnings as well as we should have. Our company has a rule that an employee has 15 days to have the treating doctor sign and return a form certifying the medical condition of the family member who is sick. We never received the signed form. The employee says that his doctor sent it. Can we terminate the employee? ...