Hi Sausagecob,
Welcome back to Virgin Media and the Community Forums!
This will be because we'll have set up a new account for you and new account number.
You will need to register for a new My Virgin Media account under your new account number using a different email address here.
Alternatively, we can merge your old and new accounts together under a process called 'move and transfer' so that you can continue to use the same email address to sign in. This can be a longer process, however please let us know which you'd prefer and we'll be more than happy to help you further.
Thanks!
Beth