I was using this Google Sheets script for putting a time stamp on the Google Sheet we use for students to check into different locations of the school. It worked for months, then randomly stopped working. If I input into the Google Sheet cell the timestamp appears, when another editor edits the cell the timestamp doesn't appear.
Why would it stop working?
Here's the script:
function onEdit() {
  var s = SpreadsheetApp.getActiveSheet();
  var r = s.getActiveCell();
  if( r.getColumn() == 2 ) { 
    var nextCell = r.offset(0, -1);
    if( nextCell.getValue() === '' ) 
    nextCell.setValue(new Date());
  }
}
 
    