I am bieng held responsible because I could not attend an appointment in the lockdown

Authorisation for me to take my grandaugter to the pediatrician was loaded from 20/09/2019 until 20/04/2020, I could only take her to the pediatrician for her check up in May, when the lockdown was brought down, as the pediatrician was only seeing children on emergencies and this was just a check up, so I could not take her in April and could take her in May, when I submitted the claim for the pediatrician, I got a response that her authorisation was only loaded until April, but I should not be held responsible for the lockdown, the claim should still be paid, since I could not take her in April, but now they refuse to pay since I could not take her in April which was not my fault