I legit can't figure out the timing. I've tried pushing it on time, I've tried pushing it early, I've even tried just mashing whatever was next until it passed
not sure how else to suggest it. Rpgmaker’s system is difficult to make this sort of game. It’ll take some effort on the players part to beat it.
However the key inputs (right, left, up, down) all work as input. Z works as input. Space works as input. Clicking on the arrows works as input. You need to click on them when they are in the green circle. They even delay half a second to allow for some wiggle room.
If all else seems to fail you can cheat the mini game by spamming space bar.