Arduino Uno as a HID Keyboard PROBLEM

Projects Programming
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  if (digitalRead(switchPin) == LOW)  // check if button was pressed
  {
    buttonPresses++;                  // increment buttonPresses count
    delay(600);                       // debounce switch
  }

You do NOT want to increment the counter when the pin IS low. You want to increment when the pin BECOMES low. Look at the state change detection example.

A 600 millisecond delay is not debouncing.