Thank you for your feedback.
Does the LP-16 displays “USB interface mode [MAC]” on the screen?
If you already created that “quit all application” script you can do the following….
Make sure the LP-16 is not selected as default input or output device under the “audio midi setting” on your mac
Disconnect the LP-16
Run the “quit all application” script
Start the USB updater
Connect the LP-16 then click on the update button
Does it working now?