Which of the following are possible reasons why the snapshot was not created?
(Choose two.)
A copy of the automated snapshot for this DB instance is in progress within the same AWS Region.
A copy of a manual snapshot for this DB instance is in progress for only certain databases within the DB instance.
The RDS maintenance window is not specified.
The DB instance is in the STORAGE_FULL state.
RDS event notifications have not been enabled.
Explanations:
If a snapshot copy is in progress for the DB instance in the same AWS Region, the system will not create a new snapshot until the copy process completes.
A manual snapshot being in progress does not prevent the automated snapshot from being created for the entire DB instance.
The RDS maintenance window being unspecified does not prevent automated snapshots from being created. It affects maintenance activities but not snapshot creation.
If the DB instance is in the STORAGE_FULL state, automated snapshots will not be created because there is insufficient storage space.
RDS event notifications are for notifying users about events and do not directly affect the creation of automated snapshots.
As I understand it, the answer is:
A copy of the automated snapshot for this DB instance is in progress within the same AWS Region.