For my situation, DMESG was posting that the USB was inserted, but nothing about loading it as a drive.
I found a post that suggested this:
sudo modprobe usb_storage
After that DMESG posted:
usb-storage: device found at 2
SCSI device sda: ...
Attached scsi disk sda at scsi0, channel 0, id 0, lun 0
I was then able to mount the drive.
To keep this permanent, I created a file called local in /etc/init.d/
I set it to executable:
and now I can mount any time I need to.
I hope this helps somebody else.