When you actually need help, probably it is. But it’s not the direct translation Duolingo asks for.
Simple ‘help!’ would translate to Polish just as pomocy! (which also is a valid cry for help), but potrzebuję pomocy! has an explicit verb for ‘need’ in first person singular. So you need to translate it as ‘I need help!’. Similarly potrzebujesz pomocy would translate to ‘you need help’ (and not just ‘help’).