Two panels comparing what the Android Publisher API accepts before and after an app has been published once. Before: uploads, listings, images and draft releases all succeed, but a completed release returns 400 and country availability reads as zero countries. After: completed releases, staged rollouts and halts all succeed.
Android

The Play Publisher API cannot make an app’s first release live — only draft releases exist until you publish once by hand

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Uploading, listings and images all work on a never-published app. Setting a release to completed returns 400 until someone presses Publish in the Console.