Update existig iOS App with different developer account?

I have been tasked to update an existing app. I'm now at the point where I would like to update to a newer version.

My previous process was to:

  1. Select my Developer Account
  2. Use "Manage Signing by XCode"
  3. Archive
  4. Upload bundle

But now I fail at 3).

The app owner has added my account within App Store Connect and made me Administrator. But when I try to upload it via XCode it tells me that the bundle id is already taken.

How do I proceed? Where do I find information on how to maintain an existing app for a different developer account?

Update existig iOS App with different developer account?
 
 
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