If you added more sign-in methods, this process will be easier. These methods may include a backup phone number, email address, backup device with the Microsoft Authenticator app registered to BlueKey MFA, etc. Login to bluekey.depaul.edu/multifactor. When asked to "approve sign-in request", click "I can't use my Microsoft Authenticator app right now" (unless you have the app on a backup device). Follow the steps to login.
If you haven't set up additional sign-in methods, contact the Help Desk. Check Help Desk hours.