Facebook is currently down, which is also causing problems for Wordfeud (due to our FB integration). We've now taken steps to isolate Wordfeud from FB's problems, but users who are logged into Wordfeud using FB may still be unable to play. Hopefully this will be resolved shortly.
@Reille78 You can download it to multiple devices as long as they all run the same operating system. But a purchase on iOS cannot be downloaded on Android and vice versa