Offline mode can only be enabled, initially, when online, either when installing the software or by visiting the software's Preferences > System Preferences > Application Preferences. Offline passcodes can only be reset after logging into the software, online or offline. Setup takes only seconds and only needs to be done once for your user account on a given computer, so be sure to enable offline mode before you need it.
For Further Reading
For more information on offline mode, view our offline guide.