In Arduino IoT Cloud, the device status describes the connection between your device and the Cloud.
One of these will be displayed for each device:
Ready to connect - The device has been properly configured but has not yet initialized a connection to the Arduino IoT Cloud.
Online - The device is connected and communicating with the Arduino IoT Cloud.
Offline - The device has initialized a connection but is not connected to the Arduino IoT Cloud.
After uploading your sketch, it may take a few minutes before the status changes to Online.