When You try to submit the application in apple store you may get following error :
Unable to process the authenticateForTransportDiscovery request at this time due to a general error. (1240)
Unable to process validateMetadata request at this time due to a general error (1019)
It happened to me too. Follwing Steps helped me to resolve it.
1. Sign Out
2. Close Application Loader
3. Sign In
4. Upload the new build again.
It works perfectly.
You don’t need to rebuild again. just re-upload works.