Most people who use automatic feeders do so only when they go on a long vacation. Although I've never used one, I understand they have less than a good reputation. Most aquarium fish can go a couple of weeks without eating, and that's usually better than having a well meaning friend dump in a half box of flakes.
If it's a new feeder, make sure all the packing materials have been removed, it has not been over loaded, and the batteries are fully charged and correctly installed. As an old man I hate to say this, but you may need to consult the instructions. Just don't tell anybody you had to resort to such a desperate, anti-testosterone measure.