Not been able to log in for 2 weeks at least - message says: -
"Your mailbox is not available at the moment.
Please retry again in one hour and make sure you are using the correct password to access your email from all of your devices.
If the problem continues, please call our team for help on 150 from a Virgin Media phone or mobile, or 0345 454 1111 from any other phone and select option 2. For details about how much it costs to call our team from a Virgin Media home phone, visit virginmedia.com/callcosts. Call costs from other networks and mobiles vary".
I take it you have not telephoned the support number?
It is a fairly common occurrence and means that your email address or account has been locked for some reason.
Please reset the password as the first step. Then it just needs Virgin Media to unlock the account to allow you to regain access.
The Forum Team (VM employees) can get that done for you. One of the team will pick up on your post (within about 24 hours) and contact you via the forum to arrange to get the necessary information from you. (Don't post your email address here.)