Time Trigger is not firing after few hours in Google Apps Script

Question

I have a script that processes email's data and saves it in google sheet. I have set a time trigger to run automatically every 15 minutes. It runs fine for few hours and then it stops working. I do not see any error or receive any notification from Apps Script; it's just like it doesn't exist. I have found these Stack Overflow questions (Question1, Question2), but I couldn't get any help from them. Removed and re-added the trigger again but same issue. Here is the sample code:

function processEmails() {
  var sheet = SpreadsheetApp.getActiveSpreadsheet().getSheetByName("Sheet1");
  var label = "InProcess";
  var msgs = Gmail.Users.Messages.list('me', { q: 'label:' + label }).messages || [];
  var LIMIT = 10, count = 0;

  for (var i = 0; i < msgs.length && count < LIMIT; i++) {
    var msg = GmailApp.getMessageById(msgs[i].id);
    var subject = msg.getSubject();
    var body = msg.getPlainBody();
    var date = msg.getDate();
    var row = [subject, date, body.substring(0, 100)]; 
    sheet.insertRowBefore(2); // insert under header
    sheet.getRange(2, 1, 1, row.length).setValues([row]);
    msg.getThread().addLabel(GmailApp.getUserLabelByName("AlreadyProcessed"));
    count++;
  }
  Logger.log("Processed " + count + " messages.");
}

And here is the time trigger panel, it's been 6 hours since the last run:

Any suggestions to resolve this strange behavior of Apps Script?

Answer 1

Why your trigger stops firing:

The issue is most likely a daily quota limit, specifically with the Advanced Gmail Service you are using. The Gmail.Users.Messages.list API call, while fast, has a separate, more restrictive daily limit compared to the standard GmailApp service. When this limit is reached, your trigger fails silently.

The Solution:

Switch from the Advanced Gmail Service to the standard GmailApp service. It's more stable for automated tasks and less likely to hit a quota limit with this type of trigger.

Here is the corrected and more robust code:

function processEmails() {
  var sheet = SpreadsheetApp.getActiveSpreadsheet().getSheetByName("Sheet1");
  var label = "inProcess"; 

  // Get up to 10 threads with the 'inProcess' label.
  var threads = GmailApp.getUserLabelByName(label).getThreads(0, 10);
  
  if (threads.length > 0) {
    threads.forEach(function(thread) {
      var lastMessage = thread.getMessages().pop();
      
      var subject = lastMessage.getSubject();
      var date = lastMessage.getDate();
      var body = lastMessage.getPlainBody();
      
      var row = [subject, date, body.substring(0, 100)];
      
      sheet.insertRowBefore(2);
      sheet.getRange(2, 1, 1, row.length).setValues([row]);
      
      // Update the labels.
      thread.addLabel(GmailApp.getUserLabelByName("AlreadyProcessed"));
      thread.removeLabel(GmailApp.getUserLabelByName(label));
    });
  }
  Logger.log("Processed " + threads.length + " threads.");
}

This code is more efficient because it fetches threads in a single call and avoids using a service that is prone to quota issues with frequent calls.