Phone not ringing

I'm in US. I just received the 1921 cable phone. Our phone line is through internet. When a call comes in the phone rings a half a ring then stops. It won't ring fully. Incoming calls are not always connecting. Outgoing calls are fine.
Any ideas?

Hello,

normally all our telephones should ring on cable/internet routers without any problems. Can you tell us briefly which Internet/telephone router your Opis 1921 phone is connected to? With this information we can help you solve the problem or send you a replacement phone if necessary.

Yours sincerely

Customer Support
Opis Technology