Norton family app Andriod

I have subscribed today with Norton family parental control. 

I have accessed my account, but I still can't my child to it. My child's phone is Galaxy s9. By the second step, where I need to fill in the codes from child's phone norton app in my account to link it. It recognizes the phone, but it doesn't register it and gives my a red x in my child's phone. I have turned on all the requested functions in my child's  phone setting, but it still not working. I tried also to log in as a parent in my child's phone, it is just the same case: it refuses any access. 

I would like here a solution please!

Thanks!