I would say you may need a pen or pin to push into button as if I remember there is nothing sticking out at the back of the 256?
So power box off push a pen or pin into hole next to the lan button but you may need a bios file on a usb.
Selecting emergency boot mode
To select certain emergency boot mode press and hold service button before the power is supplied, or in the first 2 seconds after the STB is powered on. The current mode is signaled by means of LED: each mode has a unique indication. After the specified interval (about 1 sec) is expired (you keep hold the button), the system automatically switches to the next boot mode. To activate a certain boot mode you must stop pressing the button during the required mode.
Procedure for selecting the emergency boot mode:
Unplug the STB.
Press and hold the service button.
Swith the STB power on.
Wait for changing LED indication:
Mode 1. (LED white, slow blinking). Release the button - mode 1 is activated - the STB is loaded from the first bootloader (if after the LED turns constantly white you press the button again, this can bring up the System Recovery Utility menu - when the message "Press Menu button to start Recovery menu" is appeared on the screen, you should press the Menu on RC). If you continue to hold - STB goes to mode 2 selecting.
Mode 2. (LED white, quick blinking). Release the button - mode 2 is activated. If you continue to hold - STB goes to mode 3 selecting.
Mode 3. (LED red, fast blinking). Release the button - mode 3 is activated. If you continue to hold - STB goes to mode 4 selecting.
Mode 4. (LED red, lit constantly). Release the button - mode 4 is activated. If you continue to hold - STB exit from the selection of boot modes and normal boot.
Location of service button and light indication of loading modes Emergency mode
Emergency mode is used if STB does not boot because of problems with the STB software. It is applied to download the Linux kernel (that contains System Recovery Utility) from a USB-drive or over a network using the DHCP protocol. After that you will be able to call System Recovery Utility menu and take the necessary actions for recovery (boot from an alternative NAND, reset settings or update the STB software).
To download Linux kernel the USB drive is verified first (if the USB device is readable and required file is available). If USB drive verification has failed the STB goes to receiving data by DHCP protocol.
System recovery with USB-drive in Emergency mode
Use front USB connector. The file system of the USB-drive is FAT32.
Download the uImag_mag256 file from release of MAG256;
Rename the file to Bootstrap;
At the USB drive create mag256 directory (it should be located in the root directory of the USB drive)
At the USB drive put the Bootstrap file in the mag256 directory;
Insert the USB drive into the front connector of the STB;
Unplug power supply of STB;
Press service button, turn on the power and wait until mode 4 (LED red, lit permanently);
Release the key - Emergency mode is selected;
On the remote control press Menu to bring up the System Recovery Utility menu;
Perform the necessary recovery actions (boot from alternative NAND, factory reset or update the the STB software).