> For the complete documentation index, see [llms.txt](https://docs.wproofreader.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.wproofreader.com/v6.11.0/troubleshooting/server-side-backend/application-doesnt-start-on-windows-and-iis-returns-502.3.md).

# Application doesn't start on Windows and IIS returns 502.3

### Problem

On Windows in some environments, WProofreader Application Server may fail to start in versions from `v5.38.0` to `v6.11.0`.

{% hint style="success" %}
Fixed in `v6.11.1`.
{% endhint %}

{% hint style="warning" %}
Affects Windows installations only.
{% endhint %}

### Symptoms

You may see one or more of these symptoms:

1. WProofreader Application Server doesn't start.
2. Requests routed through IIS return `502.3 Bad Gateway` because IIS can't reach the application server.
3. `Main.log` contains repeated entries like this:

```
Error    Control process failed to connect to main service process. Reason: Client exception. Connection refused. Check logs and ensure sufficient resources allocated.
```

### Solution

#### Recommended

Upgrade to `v6.11.1` or later.

To request an upgrade package, contact <support@webspellchecker.net>.

#### Workaround

Set the `AWS_EC2_METADATA_DISABLED=true` environment variable and restart the application.

Use this workaround only if you can't upgrade immediately.


---

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