Welcome to the community!
What do you mean it suddenly stopped? If you call your number does it go to voicemail or what does it do?
Did you enable call forwarding at any time? If you did had forwarding on you will have to set it up to forward back to the voicemail you can find the voicemail numbers here.
If you did nothing and it stopped working you will have to contact customer service and they can check your account and better assist you.