Why did my AP reboot unexpectedly with the “Reboot by cold start” log

Zyxel_HsinBo

A “Reboot by cold start” message indicates that the AP was rebooted due to a power interruption, meaning the device lost power abruptly rather than performing a normal software-initiated reboot.
This is typically caused by issues such as:

• An unstable or insufficient power supply device
• A faulty or aging power adapter
• Poor-quality or damaged power cables
• Insufficient or unstable PoE power from the switch or injector

When the power source fluctuates or drops momentarily, the AP will reboot and record a cold-start event.
We recommend checking the power adapter, PoE source, cabling, and overall power budget to identify and resolve the cause.