Try with keeping power button on the box pressed all the time while booting. What could be is that you have wrong image flashed to the box try to update to newest image from automatic software option and then redo the procedure with munu button to get into bios.
Let us know,
Regards,
Harry
Hi
I have flashed the image again,no success ,cant get into bios.
When then box is starting up in normal mode,the screen *Loading portal* shows a short while,then nothing happens,just black screen.I checked my Internet,and it´s ok.
I have pretty fast internet connection - 500Mbit/s