Application Loader stuck at "Authenticating with the iTunes store" when uploading an iOS app

This only started happening to me today (May 2017) and no answers in this thread solved my issue. The resolution for me was from here;

https://forums.developer.apple.com/thread/76803

Open Terminal. Change to home directory,

cd ~  

Move the current transporter directory,

mv .itmstransporter/ .old_itmstransporter/ 

Invoke the following file to let Transporter update itself.

"/Applications/Xcode.app/Contents/Applications/Application Loader.app/Contents/itms/bin/iTMSTransporter"

Wait till it updates, then open Xcode and attempt upload.

You have to agree to a new sign up in Application Loader. Select "Application Loader" under the "Xcode -> Open Developer Tool" menu (the first menu to the right of the Apple in the menu bar). Once you open Application Loader there will be a prompt to agree to new terms and then to login again into your iTunes account. After this any upload method will work.

Just wait. In a few minutes all will be ok.

Dec 10th 2019, Xcode Version 11.2.1, MacOS X 10.15.1

I was facing exactly same issue yesterday and I thought it might be network issues, at least it looks like so. But this morning I had tried couple different networks and several VPN connections, none of them is working!

The highest voted answer here asks me to reset a cache folder named .itmstransporter under my home dir, the run a program iTMSTransporter under a specific folder, but I can't find both of them.

But soon I figured that it is the cache folder for the people who uses the legacy uploader program: Application Loader, which is deprecated by Apple and can be no longer found in Xcode 11. Then I found that the latest Xcode has located iTMSTransporter here:

/Applications/Xcode.app/Contents/SharedFrameworks/ContentDeliveryServices.framework/itms/bin/iTMSTransporter

And its cache folder is here:

/Users/your_user_name/Library/Caches/com.apple.amp.itmstransporter/

I removed my existed cache folder, and run iTMSTransporter without any parameter, it soon started to output logs and download a bunch of files, and finished in 2 or 3 minutes. Then I tried again to upload my ipa file, it works!!!

CONCLUTION:

1. Either the old Application Loader, or the latest Xcode, uses a Java program iTMSTransporter to process the ipa file uploading.
2. To function correctly, iTMSTransporter requires a set of jar files downloaded from Internet and cached in your local folder.
3. If your cache is somehow broken, or doesn't exist at all, directly invoking iTMSTransporter with functional parameters such as --upload-app in our case, iTMSTransporter DOES NOT WARN YOU, NOR FIX CACHE BY ITSELF, it just gets stuck there, SAYS NOTHING AT ALL! (Whoever wrote this iTMSTransporter, you seriously need to improve your programming sense).
4. Invoking iTMSTransporter without any parameter fixes the cache.
5. A functional cache is about 65MB, at Dec 10th 2019 with Xcode Version 11.2.1 (11B500)

I was stuck at "Authenticating with the iTunes Store" today. I had used the same version and build number as a previous submission. After I updated the build number, the upload went fine. I don't know if it's related, or if it was a coincidence.