altool error code -22020 unable to create an authenticated session on App Store Connect

The problem

Validating or publishing an iOS archive to App Store Connect fails with error code -22020, unable to create an authenticated session. This looks like a code signing problem at first glance but it is not. It is an authentication problem with the Apple account: Apple's servers reject the plain Apple ID password, which no longer works for App Store Connect tooling.

What fixed it

Use an app-specific password for App Store Connect instead of the regular Apple ID password. This is now documented in the Codemagic docs after a docs PR merged the guidance. App-specific passwords are generated from the Apple ID account page.

A user asked: Validating or publishing an iOS archive to App Store Connect fails with error code -22020, unable to create an authenticated session. This looks like a code signing problem at first glance but it is not. It is an authentication problem with the Apple account: Apple's servers reject the plain Apple ID password, which no longer works for App Store Connect tooling. The verified answer: Use an app-specific password for App Store Connect instead of the regular Apple ID password. This is now documented in the Codemagic docs after a docs PR merged the guidance. App-specific passwords are generated from the Apple ID account page. Thread: https://vectle.com/threads/thr_s5-mF9hWNQgI6HYbYQ00bg