Are you SURE he's not doing it? How do you know?
Show Animation, as indicated by your screenshot, is for events, not for battle. As there IS no "this event" in a battle, you are not going to see the animation. And as you are changing the HP via a command and not the battle system itself, you also will not see a log message saying HP was increased. It's entirely possible it could be happening and you are just not seeing it.
There is a Show Battle Animation command on tab 3 of event commands that you should use instead.
You could also try setting it up as a skill to give to him when the appropriate conditions are met. That would show the animation and the text for the HP increase without you needing to do any eventing. I don't have Ace with me at the moment, so I can't check to see if you could set up an action with the appropriate conditions.