The error message Transaction refused because of an invalid argument indicates that the API rights are not set up correctly.
The merchant needs to follow these steps:
-
Log in to your PayPal account
2. Select ‘Profile’
3. Select ‘Account Information
4. Select Option 1 'Grant API permission'
5. In the field ‘Third Party Permission Username’ please fill in: development_api1.docdatapayments.com
6. Check all the boxes to grant access rights from ‘Use Express Checkout to process payments’ to ‘Issue a refund for any prior transaction’.
The email address that the merchant uses for PayPal should be registered at CM.com.