They seem to be all over the map with their docs. One section, for example, says they have no sandbox. Others give two different URIs from which you're using, neither of which respond/exist. There seems to be some split between the pro and regular interfaces.

I got code to work with the non-pro(?) production interface on v2; a couple of the details are different (no passphrase, signature is hex instead of base64). My code is quite involved though and I'm not comfortable posting it (yet). If I have time I may try to sort it out but their docs are frustrating to the point of being fairly discouraging.