Translation:You are childish!
It counted "You're being childish!" as wrong and I understand why, but in American English the circumstances where you would say "You are childish!" instead are rare.
"You're being childish!" = a behavior that needs to be changed.
"You are childish!" = a permanent condition not subject to change.
What I am wondering is is the Spanish ¡Eres infantil! truly reflect the second meaning set.