Welcome to the BT Community and thanks for your post. I have moved your post to start your own thread discussion as the thread you had posted on has already been marked as solved.
I am sorry for the problems you're having activating BT Parental Controls using your MyBT. We can pick this up from here and give you a hand to sort this out. I have sent you a private message with instructions on how you can send us over your details and we'll look into this for you. See: Private messages