Your Voice service uses Voice over Internet Protocol (VoIP) which relies on your current internet connection and local network.
Not all network devices and settings are compatible with a VoIP phone system because VoIP requires an uninterrupted internet connection to our hosted PBX servers at all times to reliably transmit calls and faxes.
If voice or fax data is lost, delayed, or mishandled by a router, it cannot be resent because it is a live conversation that is being streamed.
You may not notice network problems on your computers or other network devices because these devices are most often performing tasks that have the ability to request data be resent if it is lost, delayed, or mishandled.
For more information, see the Knowledge Base article Router/Gateway Requirements.