froze and now it won't turn on

My Sansa Clip Zip does not want to turn on neither after I held the switch on button for more than a minute and after then I released it and pushed it again. 

It’s not recognized neither by my desktop nor my laptop. 

It worked fine for a year. 

Now nothing. 

I’ve tried everything what is suggested on sandisk.com

I also held the ‘center’ button for more than 20 seconds while (and after) I connected it to a computer. It did not help. 

I would appreciate any suggestion in this subject. 

Thank you.