No sound could be several things: First: Check that the earphone/external plug is fully plugged in. Then go to the lower right hand corner, to the volume control and click on the arrow > and make sure that your device (headphones etc) is selected. If it just says input | output, make sure your Chromebook is charged. My audio buttons quit working and the volume bar stays to the left when my battery gets too low. Charge it up and then do a browser reset and a hard reset. (to do the browser reset, click the three bars in the upper right hand corner, go to settings>advanced settings >browser reset (at the bottom). Then hold the refresh button (looks like a circle with an arrow, usually the F3) and the power. This generally does the trick for me.