Ive contacted support twice about a problem and only got automated responses. Dont waste your time on this app - if they wont support it, why should you support them?
Edit: was contacted by support. If you subscribe through iTunes you need to create an NG account at their website and sign in through the app - this resolved the "Error" download button issue for me.
I do like this version of the magazine better than what I was getting through Nook.
DaveSp5 about National Geographic