> 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-nordics/t650-two-piece/errors/sdi-version-mismatch-out-of-service.md).

# SDI Version Mismatch !!! OUT OF SERVICE !!!

What to do when your T650 Two-Piece shows SDI Version mismatch !!! OUT OF SERVICE !!!

{% hint style="info" %}
**Use this page when** your terminal shows **"SDI Version mismatch !!! OUT OF SERVICE !!!"**.
{% endhint %}

<details>

<summary>Keywords</summary>

Also called: SDI version mismatch, out of service, version mismatch, software mismatch. Search terms: SDI, version mismatch, out of service, software, update, P400, T650C.

</details>

## Symptoms

You may see one or more of the following:

* The terminal shows **"SDI Version mismatch !!! OUT OF SERVICE !!!"**.
* The terminal won't take payments.

**Why this happens:** the software on the **P400** and the **T650C** doesn't match. Both units must run matching software versions to work together. This needs to be fixed by Verifone Support.

Your T650 Two-Piece has two units: the **T650C** (the unit you use to start payments) and the **P400** (the PIN pad your customer uses). The P400 gets its **power and network connection from the T650C**.

## Resolution

{% stepper %}
{% step %}

### Restart the terminal

Restart the T650C — see [How to Reboot the Terminal](/support-nordics/t650-two-piece/how-tos/how-to-reboot-the-terminal.md). The P400 restarts with it.

✅ **Message has gone — stop here.** ❌ **Message still appears — continue to Step 2.**
{% endstep %}

{% step %}

### Contact Verifone Support

<mark style="color:red;">Contact Verifone Support</mark> and tell us your terminal shows **"SDI Version mismatch"**. We'll update the software on both units remotely so they match.

{% hint style="warning" %}
Keep **both units switched on and connected** while we update them.
{% endhint %}
{% endstep %}
{% endstepper %}


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