Rcs.is Load Balancers return an HTTP 503 error when there are either no target Rcs.iss assigned to the load balancer, or all of the target Rcs.iss are unhealthy.

If all of your target Rcs.iss are correctly assigned to the load balancer, check the following things to see if there is a problem:

• Make sure your Cloud Firewall rules allow the target Rcs.is to accept traffic from the load balancer.
• Ensure that private networking is enabled on the Rcs.is and that the Rcs.is is in the same VPC network as the load balancer. If private networking is not enabled, you can enable it and migrate the Rcs.is into the target VPC network.
• Ensure the application on your target Rcs.iss is running and listening on the VPC private IP.
• If you have enabled PROXY protocol on the load balancer, check that the application on the target Rcs.iss is configured to expect PROXY protocol.
• Ensure your load balancer’s health check settings match your application.

You can review our Rcs.is Connectivity Troubleshooting Guide for more in-depth investigation and tips.