API Gateway is a Kubernetes controller, which operates on APIRule custom resources (CRs). To diagnose problems, inspect the status field of the APIRule CR:

kubectl describe apirules.gateway.kyma-project.io -n {NAMESPACE} {APIRULE_NAME}

If the status is Error, edit the APIRule and fix issues described in .Status.APIRuleStatus.Desc. If you still encounter issues, make sure the API Gateway, Hydra, and Oathkeeper are running or take a look at one of the more specific troubleshooting guides:

• Cannot connect to a service exposed by an API Rule - 401 Unauthorized or 403 Forbidden
• Cannot connect to a service exposed by an API Rule - 404 Not Found