An application running on a Compute Engine VM instance cannot communicate with an external resource outside its subnet. Flow logs and firewall logs show no denied traffic. Troubleshooting reveals:

• VPC subnet flow logs are enabled, and all firewall rules are configured to log.
• Subnetwork logs are not excluded from Stackdriver.
• The application-hosting instance can communicate outside the subnet.
• Other instances within the subnet can communicate outside the subnet.
• The external resource initiates the communication.

What is the most probable reason for the absence of log entries?