The new 4G LTE cellular communicator needed for Alarm.com service requires a firmware version of at least 1.19.3 or higher just to recognize the new cell card. If you have purchased the 2GIG-UPCBL2 cable needed to flash the GC2 firmware yourself without incurring an Over-The-Air (OTA) cellular charge from Alarm.com below is the instructions and Windows PC software needed to update your GC2 firmware. Inside the zip file is the firmware for the GC2 itself as well as firmware for the TS1 keypad if you are using one. Your current GC2 firmware MUST be at least V1.9 to use this update.
Firmware Update files (V1.19.3)
Need an update cable? 2GIG-UPCBL2.