1. Confirm whether the activation code is valid: First, you need to confirm whether the activation code used has expired or is invalid. Please check the instructions for using the activation code to ensure that the correct activation code is used.
2. Check the network connection: Please ensure that the device is connected to the Internet, because the activation code requires a network connection. If the device is not connected to the Internet, try reconnecting and activating it again.
3. Update the software: Please ensure that the AR book application has been updated to the latest version. If you use an older version, the activation code will not be available. Try updating the AR book application, and then try activating it again.
4. Contact customer service: If the above solutions have been tried, but the problem still exists, please contact the customer service support of AR Books and provide them with detailed error information and situation description so that they can provide further help and solutions.