You could try thawed frozen blood worms but 1 day or even a week without food won't kill it. It may need some time to get used to its new tank & quit fighting with its reflection. Call the shop & ask what they fed.
Oh, I see you posted while I was typing. It may be that it's sucking off the softened part of the hard pellet. Does it try to eat it again? Or is it spitting out little bits of food? Some cichlids are very messy eaters. Give it some more time & remove any uneaten food after say 20 minutes or so. You don't want rotting food left in there.