“Unknown error” during phone number verification when creating a child account

Hi All,

I wanted to create a child account, but when i need to verify my phone number i put in the text from the SMS and get this error "cannot create account - unknown error".

I've tried to create the account via family on my phone, also tried to create it on the childs phone, all with the same error.

Phones involved:

iPhone 13 - iOS 18.5

iPhone 8 - iOS 16.7.11

[Re-Titled by Moderator]

Original Title: Not able to create Child account