Before attempting to update the Symphony I/O firmware, please follow the instructions in this link:

Updating Symphony I/O Firmware and Software

 

If the firmware update fails or stalls and never completes, quit the firmware updater app, power-cycle the Symphony I/O, and try the update again, using the following steps:

– Try connecting the Symphony I/O to a different USB hub

– Try connecting the Symphony I/O to an Apple keyboard

– Try connecting the Symphony I/O to a different USB port on your Mac

– Try the firmware update on a different Mac if you have access to one

 

You may have to try the firmware update several times before it gets through. It is not recommended to try downgrading back to the older firmware versions, as the issue with the update is not with the firmware, but with the updater app itself.