I'm no expert but might be able to suggest a few things, but it depends on your situation:
What device are you connecting from/having the issue with (tablet, phone, PC, console)? Do you use a 3rd party router with the Virgin Box in modem mode or does the Virgin box give you the wireless/wired connections? What tests show fine?
Can you ping a server to test your connection? (from a Windows PC hit Start, type in cmd and press enter, the command prompt should load. Type in "ping www.google.com" without the quotes and see what comes back..
If you have a Windows PC try right clicking on the network icon in the notification area on the bottom right and select "Troubleshoot problems" and see what comes up there..
Thanks. I can't get Internet on ANY device. Using cmd prompt it just couldn't accsss Google. Everything is firmly plugged in (an earlier suggestion). The Virgin box is responsible for Internet/wifi. I've reset and turned it off and on.
The test was just the online one.
Btw the blue up/down arrow icon on the side of the box is flashing. I'm not sure it should be. The tick is constant.