Xcode Application Loader stuck at "Signing in to App Store Connect"

I experienced this issue recently.. and I seem to have found a work-around. Inside of the Application Loader.app package there's a tool called iTMSTransporter. You can invoke it from the command line to upload your package!

$ /Applications/Xcode10.1.app/Contents/Applications/Application\ Loader.app/Contents/itms/bin/iTMSTransporter -m upload  -assetFile /path/to/YourApp.ipa  -u <email@address.com> -p <password>

This is it in use in it's simplest form: for more options you can run iTMSTransporter --help upload

My answer may sound weird, I was stuck with the same issue for couple of days. Randomly on an assumption tried a scenario and that worked!

Funny thing is, my Email ID was registered under two organisational apple accounts (Developer program and Enterprise program).

• I removed myself from Enterprise account and got to successfully login to see the "Choose your app" screen.

Note: There was no issue before Apple's user roles merging activity.

Opened a bug with Apple, hoping to get this addressed soon.

Have you enabled 2FA for your account? If not enabled, Xcode won't allow adding the account.