Short answer
A panel will not arm while any protected zone is open. Find which one: on Honeywell, press * to show faulted zones; on DSC, the lit zone lights (or the LCD message) show the open zones; touchscreens list them on screen. Close the door or window, or bypass the zone, and the Ready light comes back.
On this page
Honeywell VISTA
The green READY light is off, and the keypad shows FAULT with a zone number, or "DISARMED – Press * to show faults" on alphanumeric keypads.
- Press * to scroll through every faulted zone.
- Find each one and close it: a door left ajar, a window not latched, a motion detector seeing someone walking past.
- When everything is closed, the READY light comes on and you can arm.
DSC PowerSeries
The green Ready light is off. On LED keypads the zone lights that are on show the open zones. LCD keypads say something like "Secure system before arming" and let you scroll through the open zones with the arrow keys.
Touchscreen and app-based systems
2GIG, Qolsys, Lyric, Lynx, Ring, SimpliSafe and similar systems show the open sensors on the arming screen and usually offer to bypass them.
Zone shows open but the door is closed
- Magnet misaligned. The magnet on the door must sit next to the sensor on the frame. Check that neither has fallen off or shifted.
- Motion detector. A motion zone stays faulted for a few seconds after movement. Stand still, or leave the room, and wait.
- Wired zone with a broken wire. Shows faulted permanently. Needs a technician to trace.
- Wireless sensor with a dead battery or tamper open. See sensor low battery.
Not Ready with no zone shown
If the panel will not arm and no zone is listed, check for a system trouble instead (CHECK messages, a trouble light, or an alert on screen). Some systems are set to block arming during certain troubles. See keypad trouble beeps.