What is one cause of this issue?
Request metrics for the S3 bucket need to be enabled.
S3 access logs need to be disabled for the VPC endpoints to function.
The subnet does not have the VPC endpoint as a target in the route table.
The EC2 instances need to have an Elastic Network Adapter enabled.
Explanations:
Enabling request metrics for the S3 bucket has no effect on accessing the S3 VPC endpoint. Metrics are used for monitoring, not for connectivity.
S3 access logs being enabled or disabled does not affect the functionality of VPC endpoints. These logs are for auditing and troubleshooting.
The subnet must have the VPC endpoint as a target in the route table to ensure traffic is routed through the endpoint. Without this route, the EC2 instances cannot reach the S3 bucket via the VPC endpoint.
An Elastic Network Adapter (ENA) is not required for S3 VPC endpoint access. EC2 instances can access the endpoint without needing ENA, as long as the correct routing is in place.
To the best of my knowledge, the answer is:
The subnet does not have the VPC endpoint as a target in the route table.