Without your project to look at, all I can say is check to see how it differs from the example scenes that come with HUDText (example two in particular).
HUDText's labels are also set to "resize freely", meaning they have no width or height, so there is nothing that would cause them to start a new line unless you've changed this behaviour. You can check this by pausing the game and selecting one of HUDText's labels.
Scrolling up also occurs just fine in the 2nd example.