How to Verify my sons account?

My son created an account, he is 11 years old. Now I need to verify his account but in the last step there is a technical error. I verify my card and money is temporary taken from my card but nothing is finished and verified. I was able to create a new account for him but that didn't work either as he had bought a game on his first account so he really wants help getting that account verified.

please help