Problems - Quadra through a digirig to a uSDX (8-band model)

David,
In your picture the cable is plugged in backwards - green and red connectors are intended for the transceiver side and black connector on the other end goes into Digirig’s audio socket. Connection instructions for the cable are in the product page. Though with this USDX variant I see other operators using a Baofeng cable.

Also, please keep in mind that the cable you received is audio and PTT only, there is no serial CAT connection. Unless you have a separate serial cable connected in the software you will need to disable CAT control related options (xcver in case of flrig) and configure PTT by RTS (PTT generic in case of flrig). See please see above linked post for information on establishing the serial connection.