Yes, I attached an magnet to my cover, and I'm able to use it to put it sleeping.
But something is strange, because when I have the light on and close the cover, it enters the sleeping mode but the light remains on. And, if I turn the light off, when it enters sleep it's ok, but when I open the cover again the light turns on.
It's not a physical problem because I can turn it off an on, and I removed the board and tested the button with a multimeter - is has continuity when I press the button with just a single click. So, I'm really curious about it... I tried everything, and the problem remains. Could it be something fried inside?