Software programs perform certain tasks and functions. The programs were tested repeatedly but certain sequences of events that the developers never expected (and thus not tested) can allow the software to get into a state where something is now broken.

Switching the device off and on, will reload and reset the software and generally put all settings back to its original, stable state (the state that most testing was done in) and therefore will work again. We don’t understand it either but it’s worth a try and could potentially save you time and money.