Hello,
Thank you for contacting us.
I would like to inform, that bootloader in RUT2XX and RUT9XX does not allow to use RutOS 7 or higher firmware file.
Bootloader accepts only legacy firmware, in this case - firmware version 6.8.6 file.
After that you could upgrade firmware using FOTA, file or SSH.
Hope it helps.
Best regards,
Sigitas