The first step to troubleshooting this issue is to attempt to replicate the problems. Attempt to send another test message to this user via a REST API request, or through the API Explorer in the Twilio Console.
Pay close attention to your request and double check to verify you are attempting to send messages to the correct phone number in the correct E.164 format: [+] [country code] [subscriber number including area code]
If you see similar results, continue troubleshooting with the following checklist:
Twilio's Support team can help investigate what went wrong with delivering your message. Please collect 3 or more message SIDs in your SMS logs from the last 24 hours that were flagged with Error 30005
, and open a support request.