I've finally managed to find time to upgrade from HW4 to HW6 and have got to the stage where HW is running under ilok and I'm now migrating the sample set licences. Having generated the migration request and got the file dump, the button on the following submission page suggests that I'm not logged in - although I think I am, but the "my account" button is not responsive so I can't really tell:
https://www.hauptwerk.com/prevvilicensemigrations/What to do?
As an aside, the DDoS technology on the HW webpage is immensely annoying - there are much better (and less invasive) ways of protecting against these types of attacks (i.e. hosting on AWS and using AWS shield).