Hi! I have two Mac Pro cheese graters: one 2.1 and one 5.1. They both are helping me with RED M/MX material and yes, I am still running those dinosaurs, as they are the best.
Suddenly the card in the 5.1, running Mojave, did not show up in REDcine. I have not been using it for while, thus not Shure there might be updates installed automatically, causing problems. However, I brought the other card over from the 2.1, running Snow Leopard,and it worked right away.
I put the card from the 5.1 into the 2.1 and it showed the same message in Redcine = no card in #0 position at start up and the software confirmed "no card installed" etc.
The card is appeasing the OS X hardware test and driver seems to be installed correctly.
Whe I try to install new firmware, however, the following response is show in the terminal window.

Truncated a bit...
'RED Rocket' (31111016) Current Firmware:
Are you sure that you want to continue?
Press 'y' (one card) or 'a' (all cards) and 'Enter' to continue,
or any other key and 'Enter' to abort:y
Upgrading card s/n 31111016 to firmware This may take several minutes.
Please make sure the computer is NOT powered down during the upgrade procedure.
Update failed: 'SV_ERROR_DRIVER_HWCHECK. Driver hardware check failed.'
Please SHUTDOWN fully --do not reboot-- and then power back up again.

Any clues, someone??

all the best