The use of a Virgin Media email address requires a current Virgin Media Broadband account.
Your virgin.net email address was probably set up through the now long discontinued dial-up service or the also long discontinued VM ADSL service, sold off to Talk Talk some years ago.
It's the customers responsibility to keep up to date with all VM's Terms and Conditions, and the current VM T's & C's clearly state that without a current Broadband account the email address will be deleted.
You may be able to have the account temporarily reinstated, enabling you to save any important emails, but be aware this may not be possible, and at some point the account will be closed permanently.
It's What I Do. I Drink and I Remember Things.
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