Can you tell me please your LP-16 firmware version?
Some old firmware had issue with the hidden files which generated by OSX ._
In the uTool: Settings/Target devide please make sure you select LP-16
If it is possible try to export to your USB device directly by using the “directory” option then select the USBDRIVE/Recording folder, or if not possible to access to the USB drive directly from the uTool, you can export the song to “Directory” then you’ll have to copy the “songname” folder to your USBDRIVE/Recording folder after that the player will be recognize the exported song.
When you try to update the firmware on your LP-16 please make sure you removed the USB storage device from the front panel USB connector, then connect your LP-16 to the MAC.
If you still have error please make sure to remove any other USB audio device from your MAC during the update.