I had this issue today, and in my case, it was a stupid user error. I was setting up a new product on a developer account other than my own. Bundle ID and everything was configured correctly, and I confirmed that the identifiers were created in the correct place. However, I forgot to create an App. I was in the habit of testing this out on my own account, and simply forgot this critical step on the new account. I'm sure it's not what all you lot are doing, but it's a reminder that you should at least check the status of the App in Apple Connect. If it does exist, make sure it's available. I.e, not removed.