Don't worry! Devices loose network connection from time to time but that doesn't mean your content will stop playing.
If you have already published content to a device and that devices looses internet connection, the following will occur:
The device will show as “Offline” in the devices page
It will not receive any new content from embed signage (until connection is re-established)
It will continue to playback the last set of content received, through local storage
If after 28 days your device has still not connected to embed signage, an on screen message will appear prompting you to connect the device to the internet to enable communication between embed signage and the device. You must then establish a working connection between embed signage and the device to continue using it.