I have the same problem. I can update by removing the micro SD card and connect to the computer with an adapter, Maxi PC suite does then find it and I can update. I thought the USB port was faulty but the device will connect to PC link for printing via the USB port on the unit. There seems to be an incompatibility problem with the USB port and Maxi PC Suite.
The question is:-
a) Why does the manual specify that you can update via the USB port?
b) Why is there a facility to put the device into USB update configuration (left scroll + power on) if you can't update via the port?
c) Is the client updatable via the SD card or will this be done (if necessary) via the USB port?
PS: It's a really good versatile tool, very happy with it apart from the issue above which I spent hours trying to figure out :-)