On some USB 3.0 equipped Macs, the Firmware Updater will freeze at 4% and never complete the update.

To work around this, you need to use a USB 2.0 port. This can be a USB 2.0 port on a peripheral hub, Apple keyboard, or monitor display.

 

Here are some steps to try to update your Symphony I/O:

1. Quit the Firmware Updater and power down the Symphony I/O

2. Connect the Mac side of the supplied Apogee USB Cable to a USB port on a monitor display, Apple keyboard, or external USB Hub

3. Power on Symphony I/O and run Firmware Updater ( be patient it can take up to 5 minutes to complete )

4. If your Mac does not have a peripheral connected that has a a spare USB port then you can also do the Firmware update from an older Mac with USB 2.0 as a last resort

For additional information, see this article: https://knowledgebase.apogeedigital.com/symphony-io/updating-symphony-io-firmware/