Lost emails after importing CSV contacts file from old computer

I have recently moved from a faulty computer running on Windows 7 to a new machine using Windows 8.1.  Using my Microsoft sign-in I set up Live Mail 2012 to show my Virgin Media account (@ntlworld.com) messages.  It was working satisfactorily but my contacts did not appear.  I exported a .csv file from the old machine onto a flash drive and imported it into LiveMail on the new computer.  The contacts are showing as they should but all the previously displayed messages have vanished although new messages are arriving normally.  I can view all my old messages via the Virginmedia web site so no information is lost.  Any suggestions as to how I can get Live Mail to display them again?