You do not post all your code, variable declarations are omitted, so I assume that "instruction" is of type "String" - do not use the "String" class, it will cause problems sooner or later. Your PROGMEM array "bootNotice" is declared as an array of char but assigned as an array of cstring with 1 element, it should probably have been declared without "{}" in order to be correct (you may need to use "" if you want to break lines). After "Serial.begin()" you should put in a "while (!Serial) ;" statement to ensure that Serial is up before using it. Last but not least, you need to setup the Arduino UI to use the correct type of line break in the serial monitor.