Last night my internet went off for a couple of hours - rebooting didn't make any difference. I noticed that the 'up/down arrows' symbol on the router was flashing green wheareas it is usually blue. The broadband connection came back after a few hours but today i'm having the same intermittent issues.
Looks like the hub is failing back to the legacy DOCSIS 1/2 network as it looks like a local VM network issue.
Which SH do you have?
Try rebooting the hub.
If rebooting doesn't work then you will need to contact VM for resolution, either by waiting here a few days until a VM Forum Team Member picks up the thread, or give them a call on 150 from a VM line or 0345 454 1111 for a quicker response.
On the DOCSIS 3 network (which I think you are as your traffic lights were flashing blue before) you should have 8 downstream channels and 2 Upstream channels.
If the reboot doesn't clear it then it might be worth doing a Factory Reset of the hub to clear out any gremlins in the firmware, bearing in mind that all passwords\passphrases\SSIDs will revert back to the default values printed on the hub. I have had a similar problems with the SH2 that a FR cured.