Running a function in apps script when a certain value in a range is changed to a specific Value

Question

I have this function that I use to loop thru a spreadsheet and send emails depending on the value of the status Column. I'm currently using a trigger that runs the sendEmailFunction on change in the spreadsheet.

However, I would prefer to write a programmatic trigger, that runs this sendEmailFunction when the cell value in the statusCol Range is changed from blank -> Initiate. I have tried using the onEdit(e) method, but can't seem to get it to work. Thanks

function sendEmailFunction() {
  var ss = SpreadsheetApp.getActiveSpreadsheet();
  var ws = ss.getSheets()[0];
  var totalRows = ss.getLastRow() -1;
  var statusCol = ss.getRange(2, 16, totalRows, 1).getValues(); 

  for (var i=0; i<statusCol.length; i++)
  {
    if(statusCol[i] == 'Email Sent' || statusCol[i] == null)
    {
      continue;
    }
    else
    {
      var col1 = ws.getRange(i+2, 1).getValue(); 
      var col2 = ws.getRange(i+2, 2).getValue(); 
      var status = ws.getRange(i+2, 16).getValue();
    }
  }

  if (status == 'Initiate'){
    MailApp.sendEmail('[email protected]', 'subject', 'body')
  }

}