Thank you so much for this simple explanation! I really appreciate it :) I have tried to do it following your instructions and unfortunately I keep error messages; I cannot get past the identity verification.

For reference, the first page asks for the details of my son, like name and birthday and then in the next screen I need to verify my own identity. I cannot get past this screen.

I logged in online via web browser and corrected some of my data, which I saw was outdated (expired credit card). Then I restarted my phone. However, it’s still not working.

I contacted Apple via chat and they were not able to solve it, so they asked me to contact customer support via phone call.