Twilio integration

I followed this guide: https://developer.voiceflow.com/docs/twilio-sms
I got it configured and online but when i sen a message to the number its gives out an error:
vf-sms-twilio | data: {
vf-sms-twilio | code: 500,
vf-sms-twilio | status: "Internal Server Error",
vf-sms-twilio | dateTime: "2024-01-20T08:28:29.475Z",
vf-sms-twilio | timestamp: 1705739309475,
vf-sms-twilio | data: "Program not found: 64386e21bb106b044ea34b78",
vf-sms-twilio | },
vf-sms-twilio | },
vf-sms-twilio | toJSON: [Function: toJSON],
vf-sms-twilio | isAxiosError: true,
vf-sms-twilio | toString: [Function: toString],
vf-sms-twilio | }

What could cause this?