Thanks for using the forums to get this issue with your Son's email looked into, I am sorry if this has been causing some frustration and that the other faults teams have not been successful in resolving this. I would be more than happy to look into this for you ✔
I can see you've already been given loads of help by our VIP's, thank you guys!
But you do still need a little more help with this secondary account.
From your previous posts, my understanding is that your Son's email address, which is a secondary email address, is inaccessible.
You've already tried to changed the security details however that produced the message in your screenshot, so it seems like there are so security questions set up on that email.
Just so that we don't miss anything, I've popped a helpful link here 👉 Virgin Media Email Help - Which may have more info about this issue for you or anyone else that comes across this post.
I will send over a PM now so I can take a closer look.