I recently ran into this problem after upgrading Mac OS to version 10.12 and Xcode to version 8.3.2. In the past, I had no problems deploying apps to the app store, but after the updates, my downloads repeatedly failed 15 times during the day. Closing Xcode and rebooting my macbook did not solve the problem. Typically, downloads are not performed during the iTunes Authentication phase.
In short, I ended up disabling two-factor authentication for my iCloud account, and my application loaded without errors on the first try. I believe that the error with Apple leads to two-factor authentication, which violates the iTunesConnect download process. Below are the steps to turn off two-factor authentication if you think this might solve your problem:
NOTE This is just a workaround. Ideally, Apple fixes the error, so we do not need to disable two-factor authentication to successfully download applications.
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