"Το να προσπαθείς είναι θετικό."
Translation:Trying is positive.
It should be accepted, even though the skill is about -ing forms of verbs. You might want to report it.
Don't think that's accepted because 'Το να προσπαθείς' is a gerund, but 'The attempt - Η προσπάθεια' is a noun. Furthermore, 'The attempt is positive' is not equivalent to 'Trying is positive'. The latter means the act of trying generally is positive but the former concerns a specific trial.