A. If OCI Notifications service does not receive an acknowledgement from a subscription endpoint, the service drops the message. Confirm that the subscriber is always online to receive messages to help debug the issue.

B. If OCI Notifications service does not receive an acknowledgement from a subscription endpoint, check the NumberOfNotificationFailed metric through the OCI Monitoring service for failed messages. Copy these messages to an OCI ObjectStorage bucket. Make sure the subscriber has the required credentials to access this bucket to help debug the issue.

C. If OCI Notifications service does not receive an acknowledgement from a subscription endpoint, the service tries to redeliver messages for up to one day. Make sure that the subscriber is online at least once a day to help debug the issue.

D. If OCI Notifications service does not receive an acknowledgement from a subscription endpoint, the service tries to redeliver messages for up to two hours. Configure an alarm on the NumberOfNotificationFailed metric through the OCI Monitoring service to help debug the issue.