I’m playing this game daily, but I bet you at some point I forgot to donate to my alliance. I did not forget on purpose, it just happened. I realize that You probably made this to draw people back to the game, but you could make tha auto donation feature in a way that the auto donation is only made when you enter the game. Like this:
I enter the game and the game-engine goes, was last donation more then 24 hours ago? Y/N. If yes then donate, if not then no donation.