Thanks for coming back to me and advising. Is it plugged into any extensions or direct wall socket? Also, how many pieces of equipment are plugged into it, less than 3 or more? These can be things like, other telephones, adsl routers etc
Check the phone is seated in the base unit correctly & powered ON.
Remove all other equipment connected to telephone sockets.
If possible, unplug your phone and checks 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 available then ensure the original phone is plugged into the main socket with no other pieces of equipment being plugged in.