With regards to your concern, you’ve encountered
‘USER_PERMISSION_DENIED' error. The ‘USER_PERMISSION_DENIED’ usually occurs due to incorrectly setting the 'login-customer-id’ in the request or not specifying login-customer-id in the request. Note that when a user doesn't have permission to access a customer and you’re accessing a client customer then the manager's customer ID must be set in the 'login-customer-id’ in the header request.
To resolve this, you will need to ensure that your
OAuth2 credentials were generated while logged in as the user / email address that has
access to the customer ID in your request. Also, if the said user / email address is one that has access to the MCC / manager of the customer account, then you may specify the MCC / manager account's ID as the
login-customer-id.
Furthermore, note that you received the "The developer token is not approved. Non-approved developer tokens can only be used with test accounts" error message when you tried to access the production accounts with the test developer access. It is intended to get the error DEVELOPER_TOKEN_NOT_APPROVED, since you would need to request for at least a
basic access level for developer token if you would be making calls to your production Google Ads accounts, by filling up and submitting this
application form.
Let me know if you have any question.