Resolved, the serial monitor baud rate is 1200, just I change it to 9600 or any other speed.
The problem happened when serial baud rate 1200.
it is mentioned at the device getting started page
"Opening and closing the USB Serial port at a baud rate other than 1200bps will not reset the board."
but it is just reset "restart", so why i do power off-on it didn;t load the sketch untill i uploaded again?