S : We found the easiest method of troubleshooting any possible circuit building mistakes by comparing to the schematic given on the
tutorial page. The clock might be faulty if you have sync errors when trying to upload the code onto the Arduino. If you have confirmed all the parts are wired together correctly, and the code uploads successfully, but the LED still won't blink, you probably have the code wrong. Make sure the code addresses the correct pin in which the test led is wired to. We used
this diagram.