Is this an existing phone connection that worked before but has suddenly stopped ringing?
Is your VM landline provided from the back of the VM hub or from a conventional telephone master socket?
You have posted in 'Quick Start' so would assume you are a new customer with the phone connected to the back of the VM hub?
What sort of age are the phones you are trying to connect? Older phones (early 2000s and before) may not ring when using a connection from the back of the hub.