Check your Amazon S3 bucket encryption key. AWS WAF doesn't support AWS Key Management Service (AWS KMS) keys that AWS manages. AWS WAF supports only Amazon S3 managed keys (SSE-S3) or AWS KMS for AWS KMS keys (SSE-KMS).
Verify that you have the required permissions to publish logs to Amazon S3. By default, Amazon S3 buckets and their objects are private. S3 bucket owners can use the access policy to grant access to other AWS resources.