It's possible your mail address has been closed
https://www.virginmedia.com/help/cancel-virgin-media
Cancelling at the end of your contract
If you decide to leave us after your minimum fixed term contract period, you'll just need to give us 30 days' notice.
When you cancel your services, you’ll have access to your Virgin Media Mail account for 90 days, before we close it. This should be enough time to save any contacts, emails and files.
If it's not yet been 90 days you may still be able to get support to get access to it in order to switch to another mail provider.
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I work for Virgin Media - but all opinions posted here are my own