What happens when a SEM-Honeywell/ADEMCO Vista is powered on when the system is armed?

If the SEM-Honeywell/ADEMCO Vista is powered on while the system is armed, the panel will report an empty equipment list or a SEM sync error until the panel is disarmed.

Disarm the panel locally when possible. Once the panel is disarmed, request an updated equipment list and system status. For more information about requesting an updated equipment list, see Request an updated sensor list and system status.   

If the equipment list is still empty 10 minutes after requesting an updated equipment list, the system may not be communicating properly. For more troubleshooting information, see SEM-Honeywell/ADEMCO Vista Troubleshooting Guide.