If you hear this message when trying to arm the system, there are two possibilities;
There was a previous attempt to arm which was not succcessful due to time out or a zone being left open, causing an "Arm Fail" alarm.
After an Arm Fail alarm the system needs to be disarmed before tryting to arm again. Just enter the user code on the keypad to disarm. This will allow you to arm again
The other reason could be a programmed setting which requires the Installer "Engineer" to "reset" your system after an alarm has occured.
This is due to Action 20 (require Engineer Reset) called in an Alarm Response.
Phyically Resettting the system does NOT clear the "Engineer Reset" message. This may be required for certain monitored installations in the UK. The "Engineer" has to enter the Engineer Code in order to allow the system to be "Reset", ie to arm the system.
The backup battery is low, giving a low battery warning. This prevents the system from beong armed and gives the message if the setting "Allow Low Bbattery to Arm" is not enabled
If you do not have a battery connected, then you may have a Battery Warning Alarm. You normally are not able to arm the system with a Low battery active
This is a setting that can be changed in Modules and Settings > Configuration Flag > Allow Low Battery to Arm
Reset after changing the setting