Phpmailer authentication failed but no credential changes - php

Question

I am using PHPMAILER to send confirmation emails etc. I started to get the following error 2 days ago (I thought it might just go away but seems to be an actual issue):
Message could not be sent. Mailer Error: SMTP Error: Could not authenticate.
I checked the credentials and they are ok. I am using office365 exchange login and tried to login and it works. It looks like I am on version 6.05 and the current version is 6.5 could that be the cause?
Here is what a snippet of the credentials look like:
// These must be at the top of your script, not inside a function
use PHPMailer\PHPMailer\PHPMailer;
use PHPMailer\PHPMailer\SMTP;
use PHPMailer\PHPMailer\Exception;
function tep_htmlmail($to_name, $to_email_address, $email_subject, $email_text, $from_email_name, $from_email_address) {
// Instantiation and passing `true` enables exceptions
$mail = new PHPMailer(true);
$mail->Host = 'smtp.office365.com'; // Set the SMTP server to send through
$mail->SMTPAuth = true; // Enable SMTP authentication
$mail->Username = 'email#mysite.com'; // SMTP username
$mail->Password = 'MyPassword'; // SMTP password
$mail->SMTPSecure = PHPMailer::ENCRYPTION_STARTTLS; // Enable TLS encryption; `PHPMailer::ENCRYPTION_SMTPS` also accepted
$mail->Port = 587; // TCP port to connect to
//Server settings
//$mail->SMTPDebug = SMTP::DEBUG_SERVER; // Enable verbose debug output
$mail->isSMTP();
//Recipients
$mail->setFrom($from_email_address, $from_email_name);
$mail->addReplyTo($from_email_address, $from_email_name);