Is the power LED on the board on?
yes
Is the PWR_SEL jumper on the two pins for USB?
yes
Try setting upload.verbose to true in your Arduino preferences file (you can find the location from the preferences dialog in the software); only edit the file when Arduino is not running. Then upload again, you should get more details about the process.
avrdude: Version 5.4-arduino, compiled on Aug 16 2007 at 18:09:58
Copyright (c) 2000-2005 Brian Dean,
http://www.bdmicro.com/ System wide configuration file is "tools/avr/etc/avrdude.conf"
User configuration file is "/Users/shenakan/.avrduderc"
User configuration file does not exist or is not a regular file, skipping
Using Port : /dev/tty.usbserial-A4001m2F
Using Programmer : stk500v1
Overriding Baud Rate : 19200
avrdude: Send: 0 [30] [20]
avrdude: Send: 0 [30] [20]
avrdude: Send: 0 [30] [20]
avrdude: ser_recv(): programmer is not responding
avrdude: stk500_recv(): programmer is not responding
avrdude: Send: Q [51] [20]
avrdude: ser_recv(): programmer is not responding
avrdude: stk500_recv(): programmer is not responding
Thank for your help