While trying to create a new customer account using ManagerCustomerService, please ensure that the clientCustomerID in the properties file (in case you use one of our
client libraries) or in the SOAP request header (in case you send SOAP request manually) refers to the 10 digit account ID of your AdWords manager account. You may see a ManagedCustomerServiceError.NOT_AUTHORIZED error if you use the account ID of your AdWords client account instead of the manager account. Please revert if you have additional questions.