OCI- Approved sender notfication email is not sent

Content

Customer is trying to send E-Mails from our Fusion Apps product in this OCI pod (EPPH) and usually when they set a new From address/Sender, E-Mail request for setting a new sender is sent and on clicking this link, further E-Mails have this new E-mail as the sender .

In test pod(EPPH-TEST), this worked fine but in production pod, same address doesn't get any notification and sender address is not replaced with no_reply@oracle.com.

Any idea how this can be resolved ? Customer doesn't seem to have access to this UI to set approved senders-

https://docs.cloud.oracle.com/en-us/iaas/Content/Email/Tasks/managingapprovedsenders.htm