Thanks for coming back to me. Can you do the following;
• Check the phone is seated in the base unit correctly & powered ON.
• Remove all other equipment connected to telephone sockets.
• Unplug the phone and check another phone directly into the main socket ensuring this is a VM socket and not one with a BT or Sky logo. If no alternative handset is available then ensure the original phone is plugged into the main socket with no other pieces of equipment being plugged in.