To be honest, if you get nothing on the LCD screen then that's a bad sign.
1. Try a different PSU.
2. Try connecting to TV using the composite video ports.
3. Try installing the same firmware as was on the box before it stopped working, but with the files in this post (bootargs.bin, fastboot.bin, recovery.img) also on the USB stick: http://www.futeko.com/newforum/index.php?topic=1622.msg14469#msg14469
4. Consider warranty with your reseller.
5. Try the full disassemble and forced firmware install process as at link above. Use the update.zip from the last known working firmware first, then if that doesn't work (presuming box was running Android 7) try fw version 2.0.1.