Here goes another guess:
Some modules use to come with Baud Rate of 9600 as a default. If your module is 38400 or you have changed before to 38400, ok, but if you didn´t, it´s a good bet setting up serial monitor to 9600 as a test.
Here goes another guess:
Some modules use to come with Baud Rate of 9600 as a default. If your module is 38400 or you have changed before to 38400, ok, but if you didn´t, it´s a good bet setting up serial monitor to 9600 as a test.