If your arrival date to Canada has changed, there's no need to worry, as the Canadian eTA is valid for 5 years (or until your passport expires, whichever comes first) once it has been approved. As long as you can enter Canada before that expiry date, the eTA will be valid to use.
If your eTA is expired, however, and you’d like to enter Canada after the expiry date, you’ll need to apply for another one. Feel free to reach out to us, and we’ll help you figure out your next steps.