Have you used the panel prior to this or is it completely new to you? If new and hadn’t been powered up yet that means it was powered down in an armed state.
The installer code cannot arm/disarm. You would need the master code or other user code.
The default is 1111, and you can set those when logged into Alarm.com on the users page if your panel has connected. If it hasn’t connected due to not being able to run cell test, you might try a factory reset.
Typically with that provider resets are locked out but it is worth a try. Power down the panel, hold the two face buttons, and power up (don’t need battery). Keep holding the buttons for 60 seconds, then release. Upon power up, try 1111.