Are you putting the USB stick in the rear port, on the H52tc you need to use the rear port for flashing.
If it doesn't flash, then leave the usb stick in and then once booted up press the Blue button and select flash online from the menu on the right, on the next screen press the relevant button for Local (blue button I think) and then browse to the /media/hdd/zgemma/h5/ folder and click flash. (if media/hdd is empty try /media/usb)