If you’ve added a voice-over to a path step in your presentation, it is normal behavior for the cogwheel icon to disappear. In the slightly modified menu, the Autoplay button looks like the regular Play button in any audio/video context. You can find it in the left corner of the menu.
When autoplaying a presentation containing a voice-over
You will not be able to set the timing of your path steps. They will last for 4 seconds or as long as the added voice-over. A workaround for overriding the set 4-second time interval is to add a silent voice-over that lasts as long as you would like the path step to last.
It will not automatically start playing again (loop) once it’s finished. A workaround for playing the presentation continuously is to record your presentation with screencasting software and loop the video.