what issue do you get with netinstall?
can you also connect to it via the serial connection and access the routerBOOT menu? If you can try setting the firmware to the backuploader and see if it boots from there? If it does try installing another Router OS package, update the firmware then go back to the routerBOOT menu and turn the bootloader back to use the main one again https://wiki.mikrotik.com/wiki/Manual:RouterBOOT