Three greens might suggest a faulty hub or you have no signal coming down the cable. Make sure the cable has not come loose either at the back of the hub or at the wall socket.
Try powering off the hub, wait a few minutes and power back on again. If there is no change, use the Check Service Status (top right of this screen) to see if there is a known fault in your post code area. If there's not, then you need to contact the call centre and get an engineer booked ... 150 from a VM phone or 0345 454 1111 from any other phone.
Alternatively you could wait for a member of the Forum Team to respond to your post and test the line from their end but that could take a while.