I've had the same problem 3 times with my mp3 players. I bought one first, an this happened. I contacted Sansa support, and had to send it in. They sent me a new one. This happened again, and I sent it in, and again, got a new one. The problem just occured AGAIN, and I'm fed up, lol
Hold down the power button for 20 or more seconds; when you release the power button, the Sansa Connect will restart on its own. If it doesn't restart, you did not hold down the power button long enough -- try again.
Make sure there's a battery in the player. This doesn't work when it is plugged into the USB port.
Usually answered in minutes!