DIAGNOSIS The camera has power, but it's lost its connection to your Wi-Fi network. A router reboot, a temporary internet outage, or even a slight password change can cause this.
FIX The fastest fix is to power cycle both the camera and your router. 1) Unplug the camera's power adapter. 2) Unplug your router, wait 30 seconds, and plug it back in. Wait another minute for your router to fully boot up. 3) Plug the camera back in. The solid blue light should blink during boot, then go solid. Check the app; it often reconnects automatically.
IF THAT DIDN'T WORK You'll need to re-pair it. In the Tapo app, find the offline camera in your device list. There should be a "..." or settings icon. Look for an option like "Device Settings" then "Reconnect to Wi-Fi" or "Connection Guide." Follow the prompts, which are similar to the initial setup.
HEADS UP A solid blue light means it's powered and in normal operation mode. If it's blinking blue, that's a different status—usually it's in pairing mode or starting up.