A text message sent in a campaign or from the Conversations inbox can fail due to the following reasons: 

  1. Twilio rejects the number
  2. Bad/ landline number
  3. Message not sent by Twilio
  4. Message sent but never delivered

For more information on why a particular SMS failed:

  1. Go to the Conversations tab
  2. Find the SMS message that failed. It will have a red triangle beside your profile picture
  3. Hover over the red triangle, and note the error code that shows up

  4. Here is a link to Twilio's most common error codes: https://www.twilio.com/docs/api/errors

We've found that most SMS error codes happen due to an attempt to send a text to a landline. 

If you are using your own Twilio account and have direct access to it, here are steps you can take to troubleshoot the error:

1. Log into your Twilio account

2. Click the cog icon at top-right and choose Sub-Accounts then select the sub-account

3. Click the circle icon with three dots in the left column and select Programmable SMS

4. Click Logs then set your timeframe and filter by Status = Failed or Status = Undelivered

5. When you find the message, hover over the question mark icon to see error code/explanation