Verify the IAM instance profile attached to the EC2 instances includes permissions for the target S3 bucket and Review the Amazon S3 bucket policy to ensure it allows the required actions from the instances' role are correct.

Verify the IAM instance profile attached to the EC2 instances includes permissions for the target S3 bucket is correct because when the AWS SDK runs on EC2 with no hard coded credentials the instance profile role is the identity used for requests. The role must grant permission to read the bucket objects and any required object ARNs so the SDK calls succeed.

Review the Amazon S3 bucket policy to ensure it allows the required actions from the instances' role is correct because a bucket policy can explicitly allow or deny access and it can override or restrict the role permissions. The bucket policy must permit the EC2 role to read objects or at least not contain an explicit deny.

Create a gateway VPC endpoint for Amazon S3 in the VPC is not required to resolve AccessDenied because a VPC endpoint only provides private network routing. It does not grant IAM permissions and missing a VPC endpoint usually causes connectivity errors not authorization failures.

Make the S3 bucket public so that it can be read by the EC2 instances is insecure and unnecessary. Granting the EC2 instances access with an instance role and appropriate bucket policy is the correct secure approach and making the bucket public is not recommended for tests.

Open inbound rules on the EC2 security group to permit HTTPS from the S3 service is irrelevant because the instance initiates outbound connections to S3 and inbound security group rules do not control that egress. An AccessDenied response signals permissions issues rather than security group inbound filtering.

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