Can’t create new account

Hello, 

As SWTOR has been around for a long time, it might be possible that the username you are trying to pick is already in use ... I know that numbers are not allowed in SWTOR, but I think - or _ are allowed, so it might be worth a try? 

Unavailable means it's already taken and invalid means it's not allowed (for a variety of reasons). One reason might be that you're using invalid symbols or that you're using a name or title from Star Wars or any other franchise if they're iconic to that franchise. They tend to filter those out, though it's not 100%.

In any case you'll have to keep trying till you get a display name that works. And Fenril is right about the age of the game having to do with this because the longer this game exists, the more names are taken.