The CloudBox has three different flashing Cloud LED patterns (Cloud logo on top of the CloudBox):
Solid blue light: The CloudBox is connected to power, local network, internet (Cloud Cover Music service), and is streaming correctly.
Flash, flash, pause: This indicates a connectivity issue; the CloudBox is not connected to the network. This is what you are going to see when first setting up a CloudBox, and it hasn’t yet been connected to the internet.
Flash, flash, flash: This is an API request failure. This could be where a firewall is blocking access from the CloudBox to the Cloud Cover Music API.
Long flash, long flash, long flash (about 6 second flashes): This is a media request failure. This is what you are going to see if Media is being blocked on your firewall.
For the full list of specific URL's, ports and protocols to allow through a firewall, please see this article.
Note: The status of the blue cloud logo will update when it successfully requests a song, so a temporary connection issue in between songs may cause the cloud logo to flash for several minutes until it successfully connects for the next song.
To further troubleshoot your CloudBox, please see this article.