To clarify, the Master Code and the Installer Code are two different codes
The Master Code is user code #1, associated with the primary account user in Alarm.com. This is likely the code you use to disarm as the owner.
The Installer Code gets into installation configuration menus and is needed for adding sensors, etc.
You need one or the other to get started. The Master Code can initiate the cell test required during activation.
After getting activated with us you can reset the installer code remotely through our website.