I am submitting an iOS app to the App Store using Application Loader, however, it never gets past the \"Sending API usage to iTunes Connect\" stage. There i
Are you using Xcode Organiser > Upload to App Store or Application Loader?
I found I had the same issue when going though Xcode Organiser so tried it from the Application Loader (found within Xcodes application files) and it worked just fine. If that doesn't work there is a detailed activity log you can check to get a more detailed error.
Other things to try - check your firewall settings, maybe temporary disable them. - use an alternative connection, another wifi hotspot if you are on a MacBook, if not do what Oliver said and use your iPhone's cellular data.