A few days ago, the guys at zone five software notified me that they will be switching to a new API "in the coming months". But apparently, they have already broken the old one (authentication works fine, but files won't upload anymore). I've been in contact with them but in the end they are not going to fix it.
So, long story short, until I change my apps to use the new API, you guys won't be able to upload to SportTracks. The new API has more failure cases than the old one and it will take me some time to implement the new authentication flow and test everything. It doesn't help that I'm working on these apps in my spare time. I know it sucks, but official APIs shouldn't disappear overnight like this.