It sounds like you are NOT a current VM broadband customer, is that correct?
Is it showing as active if you put the address into mailtester.com?
If yes - then try to access using an email client such as Thunderbird or outlook or whatever app is on your phone/tablet. You would need to remember the password. No guarantee this will work!
What happens if you try sending an email to the address - does it get a bounceback?
If not active, then the address and data has been deleted by Virgin in line with their T&C possibly at the normal 90 day point after your contract ended. They cannot assist former customers except to delete a problem email address.