# Error 251: Seller Not Found

PayMe's message with `language: "en"`: **Seller was not found**

The `seller_payme_id` or `seller_id` matches no seller. Also returned for an unknown public key during tokenization. Support may call this `ERR-020`.

## Usual causes

- A wrong MPL.
- A sandbox value sent to production, or the reverse.

## What to do

- Copy the MPL from **Admin → API & Integration**, and check that the key and the base URL belong to the same environment. See [Authentication](/payments/getting-started/authentication).

The full list of codes is on [Errors](/payments/getting-started/errors). If something else is going on, see [Troubleshooting by Symptom](/agents/errors/troubleshooting).