As stated, the expectation is that the native identity shouldn’t exist during the create account. You should have a native identity in the add entitlement.
What does your response mapping look like for the create account? If you are not mapping the id attribute in the response of the create, the add entitlement will still fire off, but will not have the attribute value to supply.
If your create account does not return an account id, check out this post for options to handle such case: Webservice Connector - Create Account Operation - Empty Response