Hello there!Do you have the correct board and COM port selected, you can check the COM port by opening Device Manager and going to Ports (COM and LPT) and there should be an Arduino something-something there. Make sure that COM port number is the same as the one you have in Tools->Port of the Arduino IDE.Out of curiosity, what Arduino board(s) are you using?
Are you using a USB 2.0 or 3.0 port?
Have you tried the loop-back test?
I have had some trouble with the default loopback test too. Instead of putting a wire between reset and ground, simply hold down the reset button on the board and try that way. Can you also look at the Rx and Tx LEDs to see if they blink quickly?