When I do a loopback test, the TX and RX lights both flash at the same time when I type, but I get nothing on the screen in the Serial Monitor. Also tried with PuTTY, with same results. This behavior is the same on 2 different machines. The board works on one and not the other, so that is why I am trying the loopback test. Seems odd it does not work on EITHER machine! The drivers seem to work, and the board is recognized just fine on both machines.
And if I upload a sketch to do a Serial.println("Hello!");, that works just fine, and I see the test come up in the Serial Monitor.