The device is offline or network timeout
This kind of issue is almost always triggered by connectivity problems not directly linked to our platform.
Here are a few tips that can help you solve this situation:
Check your device's internet connection and battery. Please be aware that, in order for our service to work properly, you need to have a good and stable internet connection and you need to make sure that your phone has enough battery.
Check your device is optimized to use WhatsApp in the background. Please follow the optimization tutorial here.