Unable to upload to App Store with Xcode 7.1

I've faced the same issue (account is attached to several iTunes providers) when I've downloaded Application Loader from iTunes Connect. The link on iTunes Connect download the version 3.0 of application loader that not supports multi-accounts.

To download the latest version and use multi-accounts you should download the latest version of Xcode. Application Loader is part of Xcode (Xcode > Open Developer Tool > Application Loader). You can download Xcode directly from the Mac App Store.

For more information on this delivery mechanism, see the Application Loader User Guide.

I have found a workaround to this issue. Go to iTunes connect and login with the admin itunes connect account. Create a new apple id with a new email account. Make that account the admin under users and roles.

After that sign in at least once to your new itunes connect account. Then proceed your app submission with application loader with the new account. I was facing the exact same issue and i fixed it this way!

Ben's answer notes this, but I want to call it out:

Make sure the bundle id of your app matches the expected bundle id in iTunes Connect.

This error message occurred for me when the bundle ids did not match.