Show Alert Popup when cell selection is changed (onSelectionChange)

Question

I am trying to show an alert popup when cell selection is changed, using the new trigger onSelectionChange. For some reason it is not showing any alerts. Am i doing something wrong or alerts does not work with this trigger?

function onSelectionChange(e) {
      showAlert();
}
function showAlert() {
  var ui = SpreadsheetApp.getUi();
  var result = ui.alert(
                  'ALERT!',
                  'ALERT MESSAGE.',
               ui.ButtonSet.OK);
}

I also tried that way:

function onSelectionChange(e) {
  var ui = SpreadsheetApp.getUi();
  var result = ui.alert(
                  'ALERT!',
                  'ALERT MESSAGE.',
               ui.ButtonSet.OK);
}

Answer 1

I created a script to test different ways to show a "pop up" in Google Apps Script. In both runtimes, only the one that use the HTML Service throw an error. The test was done using Chrome, a G Suite account, only signed in in one account.

Here is the code of the referred script:

function onSelectionChange(e) {
  var message = e.range.getA1Notation();
  switch(e.range.columnStart){
    case 1:
      alert(message);
      break;
    case 2:
      toast(message);
      break;
    case 3:
      msgBox(message);
      break;
    case 4:
      dialog(message);
      break;
    case 5:
      alertWithButton(message);
      break;
    default:
    console.info(message);
  }
}

function alert(message){
  SpreadsheetApp.getUi().alert(message);
}

function toast(message){
  SpreadsheetApp.getActiveSpreadsheet().toast(message);
}

function msgBox(message){
  Browser.msgBox(message);
}

function dialog(message){
  SpreadsheetApp.getUi().showModalDialog(
    HtmlService.createHtmlOutput(message), 
  'Alert'
  )
}

function alertWithButton(message){
  var ui = SpreadsheetApp.getUi();
  ui.alert(message, ui.ButtonSet.OK);
}