> For the complete documentation index, see [llms.txt](https://docs.verifone.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.verifone.com/support-uk/p400/errors/unable-to-connect-to-host.md).

# Unable To Connect To Host

The P400 can't reach the host — usually a network connection problem.

{% hint style="info" %}
**Use this page when** the terminal shows an "Unable to Connect to Host" error.
{% endhint %}

<details>

<summary>Keywords</summary>

Also called: unable to connect to host, connection error, host error, no connection, cannot connect. Search terms: unable to connect, host, connection, network, offline.

</details>

## Symptoms

You may see:

* An "Unable to Connect to Host" message when trying to process a transaction.

**Most likely cause:** the terminal has lost its network connection.

## Resolution

{% stepper %}
{% step %}

### Restart the network interface

Reconnect the terminal to the network by following [How to Restart the Network Interface](/support-uk/p400/how-tos/how-to-restart-the-network-interface.md), then try the transaction again.

✅ **Connection restored — stop here.** ❌ **Still can't connect — see below.**
{% endstep %}
{% endstepper %}

## Still not working?

{% hint style="info" %}
**Still need help? Contact Verifone Support.**

If the steps above haven't resolved the issue, [contact Verifone Support](https://my.verifone.com/s/supportbyemail). Tell us the troubleshooting steps you've already tried — it helps us get you to the right support faster.
{% endhint %}


---

# Agent Instructions
This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com.

## Querying This Documentation
If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter, and the optional `goal` query parameter:

```
GET https://docs.verifone.com/support-uk/p400/errors/unable-to-connect-to-host.md?ask=<question>&goal=<endgoal>
```

`ask` is the immediate question: it should be specific, self-contained, and written in natural language.
`goal` is optional and describes the broader end goal you are ultimately trying to accomplish on behalf of the user. GitBook uses it to tailor the answer towards what is most useful for that goal.

The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.