Tried FTP it was OK on second attempt. Again it's an issue of which username to use and which corresponding password. It's so confusing that there is a account username and a login username which is changeable. Once you are in My.Site5 using the username you choose then you need a stored password to get to next level, i.e. NetAdmin to do useful things about your domain.
Once you signed up you'll get 2 separate welcoming emails plus the one directly from the CEO. Just don't be scared by 2 completely different sets of usernames and passwords, they are both yours and very important. The set from engineering will enable you to get into My.Site5 then use the set from billing to get into NetAdmin. Once you are in NetAdmin you could change the "stored password" to something that you could remember (or something that you'll never remember, then ask tech support to reset them and start over again).
Next thing to watch is your email account setup. I setup a default email account typically as email@example.com then forwarded it to my gmail.com naturally. During WordPress installation you'll be asked to do E-mail account configuration, don't forget to write down everything you entered. If you go to NetAdmin>My Email Center>Manage Email Accounts then click the first icon (can I have tooltips for those icons please) after the email address you just setup, you will be prompted to enter password. Don't enter anything because that's the login for the Webmail which isn't working yet. If you did like me you'll be directed to an error page saying that your stored password is wrong ...etc or something like that.
Access to your webmail should be via browser at http://yourdomain.com/webmail/ (don't forget the slash at the back). It wasn't working for me in the first 10 hours or so therefore keep trying. I don't think you like using webmail but trying out all features you paid for isn't a bad idea.