Save original FW on RP-WD03


i've seen the closed topic Procedure for going back to OEM firmware for RP-WD03 but I get no output from the script.

my usb-stick has one primary partition (W95 FAT32) vfat formated and contains only the script.

I plugged the stick while the RP is Online and wait for 5 minutes and I plugged in before I start the RP.

Any suggestions?