Which of the following are possible reasons why the snapshot was not created?
(Choose two.)
A copy of the RDS automated snapshot for this DB instance is in progress within the same AWS Region.
A copy of the RDS automated snapshot for this DB instance is in progress in a different AWS Region.
The RDS maintenance window is not configured.
The RDS DB instance is in the STORAGE_FULL state.
RDS event notifications have not been enabled.
Explanations:
A copy of the RDS automated snapshot being in progress within the same AWS Region could cause the creation of a new snapshot to be delayed or blocked temporarily. This is due to limitations on the concurrent snapshot creation processes in the same region.
A copy of the RDS automated snapshot in a different AWS Region does not affect the creation of automated snapshots in the original region. The snapshot process operates independently in different regions.
The RDS maintenance window is unrelated to the creation of automated snapshots. The maintenance window is used for patching and other maintenance tasks, but not for snapshot scheduling.
If the RDS DB instance is in the STORAGE_FULL state, it may not be able to create new automated snapshots because there is not enough storage space to create the snapshot. This state can prevent snapshot creation.
RDS event notifications being disabled does not prevent the creation of automated snapshots. Notifications are separate from the snapshot creation process. They just notify you about events, including the status of snapshots.
I suspect that the answer is:
A copy of the RDS automated snapshot for this DB instance is in progress within the same AWS Region.