If your frame loses its WiFi connection, it will display a message on the screen saying "Offline." This means the frame is unable to communicate with the internet and therefore unable to retrieve photos.
The frame will continue to display photos for 24 hours without WiFi, then it will revert to the setup screen with the four numbers and a message alerting you that the frame has lost connection. This can happen if your WiFi network information has changed or if you set up the frame in one place and then move to a new location.
To reconnect the frame to WiFi, first make sure you have Bluetooth enabled on your device and you are near the frame. Open the Aura App and tap on Settings in the upper right corner of the screen. Select the frame you are using, then tap "WiFi Network." You will be prompted to enter your new network name and password.
Once you are connected, your frame should start displaying photos immediately.