If flash the firmware with the Alternative Method, you might get the text "USB drive not connected! Please insert a USB drive with a valid firmware file.".
Error name: USB not connected
Error code: #12602
This issue happens when there is an error reading the USB drive.
Make sure that the USB drive (FAT32) is connected to the printer, and that the USB port in the Buddy board is not damaged. If the error persists, try using a new USB drive.