No Audio on the RX-8200 RLS video

Although it could be cable related, the most likely reason for no audio through an SDI output is that the output routing for audio has not been set.  This is normally correctly configured during installation, but may have been lost by a factory reset.

From the Decode tab choose "Output Routing"

Ensure the SDI Embedding has been set up for Channel 1 and 2 and not to No Embedding.

Ensure you click Apply Changes to save the updated setting and then save the preset (under the Presets tab) so this change is maintained during a reboot.