I noticed there was a bug tracker for https://tracker.moodle.org/browse/MOBILE-2158.
I am testing the Mobile app on my dev site and for all my lessons, if there are more than 1 answer, the buttons are not showing. If I reduce the content page to 1 answer, the buttons show. I tried to publish a backup of the course and I also tried to create a new lesson but the problem persists. Is this a known bug? If it is, has it been fixed and published? See attached screenshots.