[Zubersoft]

It appears this is by design. If the song has multiple pages in it, I did not want the metronome to suddenly start while viewing the last page of the song and turning back to the start, because if there is a count-in or other things set, it would mess all that up. So you have two options - you can assign touch actions to "Go to Previous Song" and "Go to Next Song" (the top left/right corners, for example), and if you tap there, it would start the metronome as you expect. Or you can use the page slider or setlist window to ensure that you are jumping back to the first page of the song in the setlist that you are going to.

Mike