Hi there, I understand you want to create an S3 backup using AWS backup but you are unable to.Please correct me if I misunderstood.
The error mentioned on the notes occurs if the S3 bucket you are trying to backup has a faulty S3 event notification.
You can use the Amazon S3 Event Notifications feature to receive notifications when certain events happen in your S3 bucket.S3 offers link  and  APIs that allows you to interact with the s3 event notification feature.
I recommend you check : -Ensure that all the current S3 event notification destination still exists. -Check that all the current S3 event notification destination have a valid resource based policy. -Ensure that the KMS Key policy is valid for KMS encrypted topics and queues.For the policies follow for necessary permissions please use this link  -Add s3:PutBucketNotification to the policy arn:aws:iam::123456789000:role/service-role/AWSBackupDefaultServiceRole -Lastly ensure that the Bucket Resource Policy is not restrictive
I hope this was helpful.
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