After you changed your Wi-Fi password, or Wi-Fi Name (SSID), or your router, your device in that network will show Offline. Here's how you can bring it back online.
1. Select the Device setting icon of the offline device in the Homepage
2. Select General
3. Select Wi-Fi setting
4. Follow the in-app instructions and make sure you enter a correct password for your Wi-Fi network.
Your device should get back online again if the WiFi password entered correctly.