Auto advance slides every 15 seconds (only working for 1st slide)

I am giving an 'Ignite' talk, the rules for which state that there must be 20 slides which auto-advance every 15 seconds.

I am trying to get this to work in Keynote 6.5 on Yosemite. I have tried the following settings, applied to all the slides:

And for the Document:

However, when I start the presentation only the first slide auto advances after 15 seconds, the following slides only respond to a click or cursor key press. How can I make all the slides behave like the first slide?