Topfin auto feeder doesn't work
Unfortunately, many autofeeders have a distressing habit of dying without much use time. Topfin is PetSmart's house brand and while you can ask them about it, if it's not still under warranty, I doubt they can help. They don't seem to carry parts for Topfin or Great Choice products.
I like the Eheim auto-feeders myself, they seem to last reasonably well.