The error message you're seeing is from the Twilio API, indicating that the account being used to send an SMS message does not have permission to send messages to the phone number region specified in the 'To' field.

To resolve this issue, you should:

1. Check the Twilio Geo Permissions: Twilio controls which geographic regions you can send SMS to through their Geo Permissions settings. You need to log into your Twilio account, navigate to the SMS settings, and ensure that the geographic region for the number you are trying to send an SMS to is enabled.

2. Verify Your Twilio Number: Make sure that the number you are using to send SMS messages is correctly set up in your Twilio account and has the necessary permissions.

3. Check Twilio Account Status: Ensure that your Twilio account is active and in good standing. If your account is suspended or there are billing-related issues, it could prevent SMS messages from being sent.

4. Review the 'To' Number Format: Ensure that the 'To' number is in E.164 format, which includes a '+' followed by the country code and the full phone number.

5. Check Twilio Account Balance: Sending SMS messages via Twilio requires a positive balance in your Twilio account. If you do not have enough funds, the message will not be sent.

6. Contact Twilio Support: If you've checked all the above and still encounter issues, you should reach out to Twilio's support for further assistance.

7. Review Twilio Documentation: Twilio provides comprehensive documentation that can guide you through the process of setting up SMS permissions and troubleshooting common issues.

Make sure to follow these steps to resolve the sending issue. If the problem persists, you may need to engage with Twilio support for a resolution specific to your account and setup.