I have stopped using Nike+ and didn’t notice that Nike has redone the Nike+ service, and a couple of weeks ago my plugin to download Nike Activities as TCX and GPX files, stopped working.
I was expecting this for a while, since I was essentially calling their unpublished APIs. I have taken a quick look at it and there is good and bad news.
The bad news is, the changes are major. It will require a rewrite.
The good news is, there is now an official API.
I have the code deployed on github @ https://github.com/jkili/nike-gpx, so am happy for someone to pick up the work at moving the plugin code to the API (it looks very do’able). However, I note there are heaps of Nike+ GPX tools out there so I don’t think it is worth the time investment from my perspective.
I am sorry to everyone who has used the tool and become reliant on it, but check out one of the other tools and hopefully it fulfills your needs.
Continuum 
Thanks for all your hard work. It has been much appreciated by many including myself.
Appreciated Brad