> ## Documentation Index
> Fetch the complete documentation index at: https://devzone.nayax.com/llms.txt
> Use this file to discover all available pages before exploring further.

# Error Handling & Troubleshooting

This page covers system-level issues: terminal registration, configuration, and log collection. For SDK-level integration issues (serial setup, threading, callbacks, memory), see [Integration Guide](/docs/integrate-pos-device/emv-core/rtos/rtos-integration-guide#integration-troubleshooting).

When encountering errors or unexpected behavior, provide the following to Nayax support:

1. **Device ID** (Reader Serial Number)
2. **EMV Core FW version** in use
3. **EMV Core configuration file**
4. **EMV Core log files**
5. **Transaction data** (if applicable): date/time, amount, transaction ID, error received
6. **Reader configuration** (retrievable with the Saturn Management Utility)

## Log Files

The EMV Core saves information in log files for debugging purposes.

Log files can be obtained by:

1. **Nayax Core**: Use the **Request Gtrace** action.
2. **TMS**: Send the `UPLOAD_LOGS` command.
3. **Locally via UNO-8 Manager**:
   * Select the **File System** tab.
   * Navigate to the `E:\LOG` folder.
   * Right-click the `*.log` files and select **Save As...** to save to your PC.

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  <img src="https://mintcdn.com/nayax-44d6e37b/mqSvbg9R3CfdCY1b/images/docs/rtos-troubleshooting/log-files.png?fit=max&auto=format&n=mqSvbg9R3CfdCY1b&q=85&s=4b7adf2173f716df5030dcd6975e0c2a" width="925" height="497" data-path="images/docs/rtos-troubleshooting/log-files.png" />
</Frame>

## Troubleshooting Sequence

When encountering an issue, work through these steps in order:

1. **Check SDK version**: Uninstall old versions and install the latest.
2. **Check and update configuration**:
   * EMV Core configuration
   * Reader configuration
3. **Verify correct registration**:
   * OTI TMS
   * Nayax Core
   * Note: Test terminals and live terminals require different registration.
4. **Try a transaction with a valid test card.**
5. **Ensure communication is not blocked by a firewall** or similar mechanism.

## Common Problems

### Error Code Overview

Error codes fall into two categories depending on their source:

* **Positive error codes** (e.g., `99`): From the PSP system.
* **Negative error codes** (e.g., `-997`): From the OTI system.

Note: Negative error codes such as `-995 declined by reader` can also indicate an online decline from the PSP.

***

### Terminal Registration Issues

**Symptom 1:**

* Status = `Not ready` (visible in the test application "Get Status" button)
* Error: `"Failed getting terminal operator …code: -997"`

**Possible cause:** Terminal is not registered properly in TMS.

**Suggested steps:**

* Confirm your terminal ID appears in TMS under the correct operator; consult Nayax support if needed.
* Check the EMV Core configuration file for:
  * `TMS_SVC_URL=tms.otiglobal.com` (for management from TMS)
  * `TMS_SVC_URL=tms-c.otiglobal.com` (for management from Nayax Core)

***

**Symptom 2:**

* Transaction ends with error:
  ```
  Method TransactionComplete arrived with parameters: Declined '1' Invalid Device' {...}
  ```

**Suggested steps:**

* Check the kiosk configuration file. Most common settings:
  ```
  PAYMENT_SVC_URL=payment-nayax-p.otiglobal.com
  ```
* Verify the terminal ID is properly registered at Nayax backend; consult the Nayax support team.