Serial communication over USB not working

I uploaded the example main_serial for the Shieldbuddy and tried to send input with the serial monitor in the Arduino IDE and with HTerm. When I input anything the answer should have been the input but I didn't receive anything. After exchanging SerialASC.write() with SerialASC.print() all I'm receiving are a couple of 0x00 bytes.

Port and baudrate should be fine and another computer with working installation receives the correct answer so the upload from my computer is also working just not the communication.

I hope anyone has a solution for my problem!

greetings