5. Prepare USB Stick FAT32 formatted and copy Firmware to USB Stick.
Example: OCTAGON_SX88_FW_v1.04.56_20180409.mupg
6. Connect USB Stick with Receiver.
7. Remote Control: Press Red Button and select Firmware file.
8. Start with OK button and wait installing.
Good Luck, Repair should be done !
OCTAGON SX88 & SX88+ Download:
https://www.octagon-germany.eu/downloads/digital-receiver/hdtv-receiver/
OCTAGON GERMANY Support
https://www.octagon-germany.eu
http://octagon-forum.eu