Do you see the little lightning/zap symbol next to the “like” button? If not, double check that you’re on the latest update of Damus. If you already are, then try force closing the app and reopening it. To force close it, swipe up on your screen halfway, into the app switcher. Then swipe the Damus preview up and off the screen and reopen. When I first setup zaps I had to do that and it worked.