We have a Spark Max that functions normally in every way, except when we connect it by USB to the Rev Hardware Client, we do not see the rest of the CAN bus. We can connect to another Spark Max by USB, and see the whole CAN bus, including the Spark Max with the mysterious problem.
Check the firmware version and make sure REV H/W Client is current. Be sure that the CAN ID is set to something unique. It does seem to be an odd problem!
Things I would try here:
Check your CAN bus wires, sometimes a short will cause mismatch in IDs
Check firmware on CAN spark if the old firmware is causing can spark not to read at all could be showing two different “networks”
Check CAN leds for further errors
Swap the Can spark ID and see if issue persists
Definitely a weird problem especially since you are still able to operate the Can spark motor normally
Hope you solve it Im sure you can!