Turn on denonavr receiver when a source is changed (#44473)

homeassistant/components/denonavr/media_player.py

@@ -338,6 +338,9 @@ class DenonDevice(MediaPlayerEntity):
 
     def select_source(self, source):
         """Select input source."""
+        # Ensure that the AVR is turned on, which is necessary for input
+        # switch to work.
+        self.turn_on()
         return self._receiver.set_input_func(source)
 
     def select_sound_mode(self, sound_mode):