To test the Payment Gateway:

  1. Go to Core > Settings > Payment Settings > Payment Services
  2. Verify that the log in credentials have been entered correctly.
  3. Go to the Event Registration form and click Edit 
  4. Select Registries in the left column
  5. Check the Show Failed check box
  6. Select View to see failed attempts
  7. Click into it and if "Security header is not valid Error code:10002" shows, this is an error code that comes from Paypal and is a good indication that it is a Paypal login credentials issue.
  8. See this reference on Paypal Error Codes.
  9. Contact Paypal and confirm all credentials being entered are matching up with what Paypal has.

Steps to solve the problem:

  1. Verify the Payment Gateway credentials (Account Login and Password) are correct.
  2. If credentials are correct, try to test on a different browser or clear cache.
  3. The correct API credentials must be updated in the system and a Paypal Payments Pro account needs to be set up in order to sync it, not just a regular business account.
  4. Test processing a registration payment once the credentials have been corrected.