Hi @DrChuck,
Based on the information you provided, I think the core problem is that your fax number is configured as part of a voice rollover group. This is a common issue with new RingCentral setups. The system's call handling rules for voice calls conflict with the specific digital tones required for a fax transmission, causing the faxes to fail.
The definitive solution is to remove your fax number from the rollover group and assign it to a dedicated "Message-Only Extension" within the RingCentral Admin Portal. This creates a specific pathway for faxes that bypasses all voice routing, allowing transmissions to be received correctly.