Resolved ERROR: unable to locate firmware file on USB device
Followed the instructions below and a progress bar appeared <re: firmware> then followed by a normal startup.
Now I can go change my underwear.
I got this info from https://www.soundside.de/support/KPARecovery.htm
Other useful Kemper recovery solutions as well.
Install or reinstall the firmware
• Switch the main knob to off
• Download the latest KPA firmware
• Get an empty fat32 formated USB stick
• Copy the unziped firmware file 'kaos.bin' to the root folder of the USB stick
• Plug the USB stick into the KPA
• Press and hold both '<' and '>' keys
• while still holding both keys - switch KPA to tuner
• Something like 'booting and installing' will be displayed
• Wait until the firmware is reinstalled