I have been successful sending a SMS message from my North American Twilio number to a North American number. When I add a UK number the log says that it is not a valid phone number. Is that an integration issue or how I setup my Twilio account?
twilio.base.exceptions.TwilioRestException: HTTP 400 error: Unable to create record: The 'To' number 447redacted (12 digits) is not a valid phone number.
I lost my UK number so not an issue for me anymore. I was unable to determine if it was a Twilio policy to serve only domestic market or a restriction in the HA integration code. Twilio operates in the UK so I imagine there would be no policy restrictions sending a message from your UK Twilio number to other UK number. If you can read code, the Twilio integration source code is on GitHub.