Google sheets script sending twilio SMS messages w

I am trying to build a google sheets spreadsheet to send SMS reminders. At this stage, I'm still just building the basics of sending SMS from google sheets. I have replaced some fields with their names, eg the API SID and token, and my phone number. My code is below:

//At the moment this seems to work when manually run, but not when triggered by time or whatever.


function sendSms(to, body) {
  var messages_url = "https://api.twilio.com/2010-04-01/Accounts/API_SID_GOES_HERE/Messages.json"; //This contains my Twilio API LIVE SID
 
  var payload = {
    "To": to,
    "Body" : body,
    "From" : "61123456789" //This is the twilio phone number
  };
 
  var options = {
    "method" : "post",
    "payload" : payload
  };
 
  options.headers = { 
    "Authorization" : "Basic " + Utilities.base64Encode("API_LIVE_TOKEN_GOES_HERE") //This contains my Twilio API LIVE Token
  };
 
  UrlFetchApp.fetch(messages_url, options);
}
 
function sendAll() {
  var spreadsheet = SpreadsheetApp.openById("SPREADSHEET_ID_NUMBER") //This part is the ID number of the spreadsheet
  var sheet = SpreadsheetApp.setActiveSheet(spreadsheet.getSheets()[2]); //This little feller sets an active sheet which it manipulates. Sheet count starts from [0]
  var startRow = 2; //starts counting from row #2
  var numRows = sheet.getLastRow() - 1; 
  var dataRange = sheet.getRange(startRow, 1, numRows, 2) //getRange(Integer row, Integer column, Integer numRows, Integer numColumns)
  var data = dataRange.getValues(); //Gets just the values of the cells, not the formulas
 
  for (i in data) {
    var row = data[i];
    try {
      response_data = sendSms(row[0], row[1]);
      status = "sent";
    } catch(err) {
      Logger.log(err);
      status = "error";
    }
    sheet.getRange(startRow + Number(i), 4).setValue(status); //The number after (i), is the column where the setValue(Status) will land.
  }
}
 
function myFunction() {
  sendAll();
}

It seems that if I run the code manually, it works fine, sends an SMS, updates the 'status' field and all is well. However, if I set a trigger for the script, be it a fixed time trigger or an every minute trigger, the script fails. The Summary of Failures that google apps script sends me is:

Request failed for https://api.twilio.com/2010-04-01/Accounts/MY_ACCOUNT_NUMBER/Messages.json returned code 400. Truncated server response: {"code": 21211, "message": "The 'To' number is not a valid phone number.", "more_info": "https://www.twilio.com/docs/errors/21211", "status": 400} (use muteHttpExceptions option to examine full response) (line 19, file "Code")

I can't quite figure out why. I think it has something to do with var spreadsheet and var sheet, but I really don't know.

Most of the code has been copied from this twilio blog post.

I figured this out, and it was something terribly obvious.

When setting up the trigger, I had completely overlooked the need to define which function I wanted it to trigger. By default, it was just running function sendSMS, which, at that point, had not been fed any data to send.

So my manual runs were running the function called myFunction, but the triggered runs were running sendSMS.