Serial.print does not appear to print

I'm a new Arduino user working through the Arduino Projects. I'm currently on Project 3.

Line 12 of the code is Serial.print("Sensor Value: ");

The issue is that when I run the code I do not see this message, or any others. I expected to see it in a command prompt window on the PC that is connected by USB to the Arduino board.

I have tried this using the code from the Files/Examples/StarterKit, so I don't think mine is a code error.
The code contains under Setup, Serial.begin(9600);
The Arduino board seems to be working fine. Project 3 is displaying LEDs showing the temperature just like it should.
I have tried manually opening a command prompt window, and closing all windows except for the Arduino window.

My PC is running windows 10.

Thanks for any suggestions.

There is a small magnifying glass icon in the IDE window that has to be clicked to open the serial monitor.


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DanMarshall:
Line 12 of the code is Serial.print("Sensor Value: ");

You should always post a complete program.

Is there a line Serial.begin(9600); in setup()? Note that the number may be different.

...R