# The app does not run

URL: https://getflowing.ai/docs/troubleshooting/app-not-running

Your app built and deployed on GetFlowing but crashed or failed its health check. The usual causes, and how to fix each one.

> Your app was built and deployed, but it isn't running correctly yet. The agent can look at this for you.

The image built, but the app crashed, or never passed its health check. On a plan with the agent, ask it in the app's chat. Otherwise, read the app's logs on its **Health** tab, and check the usual causes:

- **It listens on `localhost`.** Listen on `0.0.0.0`.
- **It listens on another port.** Listen on the port in `PORT`, which is 8080, and do not set `PORT` yourself.
- **Nothing answers at `/`.** `GET /` must answer with a status from 200 to 399 within 5 seconds. An API with no route at `/` sets a path it answers on, such as `/health`, in the app's **Settings**, under **Health check**. A `404` is never healthy.
- **It starts too slowly.** It has 60 seconds to start. Move slow work, such as a large migration, out of start-up.
- **It runs out of memory.** It has 512 MB.
- **A variable is missing.** Check the app's variables for any marked **missing**, and set them in the app's Settings, under Variables.

See [What every app needs](https://getflowing.ai/docs/build/app-requirements).