Faxing is a sensitive thing. While Fios which is fiber optics, is good for data, it may not be that good for equipment that depend on a certain signal type. Each time a fax phone rings, the fax checks the signal to verify if it is a phone call or fax call. This determination is verified by a fax tone on the line. You may also experience connection issues that are fax dependent. Sometime the Fios signal is converted to copper and this conversion does have an adverse affect on you signal-to-noise ratio.
Your options are:
1. Dedicated copper phone line service or
2. Consider a Fax Thru Email service such that can send and receive.
