Migrating SiwA users after app transfer

We recently transferred our app from one developer account to a new one, internally. We're trying to transfer our sign in with apple users, but have hit a snag on the first step.

I'm following the instructions here to "Obtain the user access token": https://developer.apple.com/documentation/sign_in_with_apple/transferring_your_apps_and_users_to_another_team

This is my request as created in postman:

curl --location 'https://appleid.apple.com/auth/token/'
--form 'grant_type="client_credentials"'
--form 'scope="user.migration"'
--form 'client_id="com.XXXXX"'
--form 'client_secret="XXXXX"'

No matter what I try, I always receive invalid_client.

I've uploaded example JWTs in FB15648650.

Migrating SiwA users after app transfer
 
 
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