If your temporary status in Canada (e.g. your study permit) has expired and you did not apply for an extension before the expiry date, you must apply to restore your status within 90 days of the expiry date if you want to stay in Canada. This process is known as restoration of status. See this site for more information on restoration.
On May 21, UBC will move to a new system called Workday for courses starting in September 2024. Check your email that day for setup instructions. Summer Session students will continue using SSC.