I've tried to use virtual account number and it will just not work for me. Not sure if it's user error or what, but when I sign in it tells me my user name or password is wrong (it's not). No one at Citi seems to be able to explain why or fix it. But I digress....
I had this problem at first too so I changed my password to remove the special characters (now uses only letters and numbers) and now the VAN login works fine. So for me at least, it appears to be that the VAN subsection can't properly recognize special characters in the password.