Users are reporting an outage on your public-facing application that is hosted on Compute Engine.

Enable Firewall Rules Logging on the latest rules that were changed. Use Logs Explorer to analyze whether the rules are working correctly.

Connect to a bastion host in your VPC. Use a network traffic analyzer to determine at which point your requests are being blocked.

In a pre-production environment, disable all firewall rules individually to determine which one is blocking user traffic.

Enable VPC Flow Logs in your VPC. Use Logs Explorer to analyze whether the rules are working correctly.