Troubleshoot readiness check

get-started/troubleshooting.md

@@ -715,6 +715,35 @@ cf logs <appname> --recent
 If you omit the option `--recent`, you can run this command in parallel to your deployment and see the logs as they come in.
 :::
 
+### Why do I get "404 Not Found: Requested route does not exist"?
+
+In order to send a request to an app, it must be associated with a route.
+Please see [Cloud Foundry Documentation -> Routes](https://docs.cloudfoundry.org/devguide/deploy-apps/routes-domains.html#routes) for details.
+As this is done automatically by default, the process is mostly transparent for developers.
+
+If you receive an error response `404 Not Found: Requested route ('<route>') does not exist`, this can have two reasons:
+1. The route really does not exist or is not bound to an app.
+  You can check this in SAP BTP cockpit either in the app details view or in the list of routes in the Cloud Foundry space.
+2. The app (or all app instances, in case of horizontal scale-out) failed the readiness check.
+  Please see [Cookbook -> Deployment -> Health Checks](../guides/deployment/health-checks.md) and [Using Cloud Foundry health checks](https://docs.cloudfoundry.org/devguide/deploy-apps/healthchecks.html) for details on how to set up the check.
+
+::: details Troubleshoot using the Cloud Foundry CLI
+
+```sh
+cf apps # -> list all apps
+cf app <your app name> # -> get details on your app, incl. state and routes
+cf app <your app name> --guid # -> get your app's guid
+cf curl "/v3/processes/<your app guid>/stats"
+  # -> list of processes (one per app instance) with property "routable"
+  #    indicating whether the most recent readiness check was successful
+```
+
+See [cf curl](https://cli.cloudfoundry.org/en-US/v7/curl.html) and [The process stats object](https://v3-apidocs.cloudfoundry.org/version/3.184.0/index.html#the-process-stats-object) for details on how to use the CLI.
+
+:::
+
+
+
 ## CAP on Kyma
 
 ### Pack Command Fails with Error `package.json and package-lock.json aren't in sync`