Configurations needed to allow for AP Invoicing through OBN

Hello Experts,

I am trying to determine all the steps needed to allow suppliers/vendors to send AP invoices to EBS from OBN. What I have so far is below. However, in OBN the Self Testing is ending with ERROR.

1. Create a URL so that OBN can access our EBS R12 instance (EG: https://www.<server name>:<port>/webservices/TransportAgentServer)
   1. This is complete
      1. URL: https://api.xyzcompany.com:443
2. In EBS: Configure User
   1. This is complete
      1. Username: XYZEBSOBN
      2. Password: *********
3. In EBS: Configure "XML Gateway > Define Trading Partners"
   1. This is complete
      1. Transaction Type: AP
      2. Transaction Sub Type: INI
      3. Standard Code: OAG
      4. External Transaction Type: INVOICE