There are many pieces involved in getting a program onto your Arduino board, and if any of them aren’t right, the upload can fail. These include the drivers for the board, the board and serial port selections in the Arduino software, access to the serial port, the physical connection to the board, and more.
The first thing you should check is whether you have the correct Arduino selected when using the Arduino IDE programming software. In the Arduino IDE software click on Tools>Board and verify that you have selected the same board you are using.
The next thing to check is the port you are using to communicate to the Arduino. Look in the Tools > Serial Port menu. If your port doesn’t appear, try restarting the IDE with the board connected to the computer.
On the Mac, the serial port should be something like /dev/tty.usbmodem621. On Linux, it should be /dev/ttyACM0 or similar. On Windows, it will be a COM port but you’ll need to check in the Device Manager (under Ports) to see which one.
If you don’t seem to have a serial port for your Arduino board, we recommend first reinstalling the IDE. Sometimes this will ensure that the right drivers are in the right place. Beyond that please refer to www.arduino.cc and search on “Why can’t I upload my sketch to my Arduino?” or contact us by phone or email firstname.lastname@example.org.